Haruchiyo Sanzu - Blog Posts

Sanzu's new birthday card art, his birthday sign and a full look at his outfit!

This is my favorite manga panel:

Ran’s all like…

“oh really?” WHAMM

𝐁𝐎𝐍𝐓𝐄𝐍'𝐒 𝐍𝐔𝐌𝐁𝐄𝐑 𝐓𝐖𝐎

— sanzu haruchiyo x fem!reader

PART ONE 4.9k words

short summary. in which your heartbreak over Mikey pulls you into the dangerous and irresistible orbit of Bonten's Number Two, Haruchiyo Sanzu. warnings. sanzu haruchiyo is his own warning, graphic violence, substance abuse, toxic/manipulative relationships, explicit sexual content, depression & self-destructive behaviour, strong language. tags. female reader insert, bonten au, tsundere!sanzu, ex-boyfriend!mikey, angst with a happy ending, slow burn, heavy pining/yearning.

masterlist

Manjiro Sano once promised you forever. He'd said it so easily back then, like it was a given, something as natural as breathing. You were fifteen, standing by the riverbank after another reckless night, his blonde hair glowing under the streetlights. He had to tilt his head up to meet your eyes then, his expression so open, so sure.

"It's you and me, always."

Now, nearly ten years later, that memory feels like a lifeline in the middle of a storm. You hold onto it so tightly that your knuckles turn white. It's the only thing keeping you grounded as you stand in the shadowed corner of a chapel, watching him slip a ring onto another woman's finger.

The bride is stunning, of course. Her white gown flows around her like something out of a dream, her face set in a serene mask of duty. And Manjiro—Mikey—he looks... distant. Like he's not even there, going through the motions, his face unreadable, hollow. It's a mask you've seen him wear too many times now, a defense mechanism, something to protect the broken parts of him he never lets anyone see.

You sip your wine slowly, the bitter taste doing little to mask the bile rising in your throat. A strange mixture of dark satisfaction and aching sadness twists inside you, an uncomfortable knot of emotions you can't quite unravel. 

He doesn't love her, you remind yourself. He's still yours. He promised.

But the truth is, the wine does little to dull the sharp edge of betrayal. The ceremony feels like a bad dream, one you can't wake up from. 

It's a sham. Just a business arrangement, nothing more. A duty to his late brother Shinichiro, who made a deal with her family long ago, a deal Mikey feels bound to honor. You respect that, you always have. His loyalty is part of what made you fall for him all those years ago.

But it still feels like a knife in your chest, twisted with every vow spoken. You won't question it though. You can't. Because questioning it would mean questioning Shin's memory, and that's something you'll never do. Still, the pain lingers, like a bruise you can't stop pressing on.

As the ceremony ends and the couple walks down the aisle, Mikey's eyes meet yours, even from across the room. For a brief moment, his lips curve into that familiar soft smile, the one that's always been just for you, full of unspoken words and old promises. It's enough to settle your nerves, if only slightly. 

He's still yours, you remind yourself again. This doesn't change anything.

The guests start to shuffle toward the reception hall, but you hang back, feeling the taste of the wine and the weight of the day pressing down on you. The laughter and chatter fades as you step into a quieter hallway, seeking a moment of solitude, a reprieve from the overwhelming noise of celebration.

But you're not alone. A figure leans against the far wall, tall and lean, with faded pink hair that you'd recognize anywhere.

Haruchiyo Sanzu.

Of course, he'd be here. Even though no one from Bonten was supposed to attend, you should've known Sanzu would show up, disregarding protocol like he always does. He's dressed in one of his garish purple suits, the cigarette in his hand burning slowly as he takes a long drag, his katana resting lazily against the wall next to him. The sight of it makes you roll your eyes despite the situation. How he manages to carry that damn thing everywhere without someone calling the cops on him is beyond you.

He doesn't even look at you as you approach, though you know he's aware of your presence. Sanzu's always like that—aloof, unreadable, like he's waiting for something but never telling you what.

Your heels click against the marble floor, the sound too loud in the silence, as you stop in front of him. You cross your arms, defensive. 

You've never liked him. Not since the beginning. And he's never made an effort to hide the fact that he feels the same way about you. His disdain has been obvious for years now—cutting comments, backhanded remarks. Always just subtle enough to avoid Mikey's wrath.

"You shouldn't be here, Number Two," you say, your voice sharp, cutting through the haze of tension.

Sanzu exhales a slow stream of smoke, not bothering to meet your gaze as he taps the ash onto the floor, a flick of his wrist that seems deliberate in its carelessness. 

"Neither should you," he replies, voice lazy, eyes flickering toward you briefly before he adds, with a smirk, "Mistress."

The word lands like a punch to the gut. You stiffen, your chest tightening as anger flares hot and fast inside you. You want to snap back, to tell him to fuck off, but you hold it in, forcing yourself to stay composed.

Sanzu's teal eyes slide back to you, and there's a gleam in them that you hate—a predatory gleam, like he's enjoying this far too much. He tilts his head, studying you like you're something amusing, something to poke and prod until it breaks.

"What's the matter? Cat got your tongue?" His voice is smooth, laced with mockery. "You know, it's almost cute. The way you're still holding out hope. Like he's going to drop everything and come running back to you."

Your jaw clenches, but you don't give him the satisfaction of a reaction. You've dealt with Sanzu long enough to know better than to let him get under your skin. He feeds off that kind of thing, turns it into a weapon.

"Shut up," you bite out, your voice low, controlled. "You don't know a damn thing about us."

That earns you a smirk, his scarred lips curling into something cold and twisted. "Don't I?" He takes another drag of his cigarette, exhaling slowly as if savoring the moment. 

"I know enough. I know he's up there, at the altar, with his wife, while you're out here clinging to whatever scraps he throws you."

You feel your fists tighten at your sides, nails biting into your palms. The urge to slap that smug look off his face is overwhelming, but you know better. You've learned that lesson the hard way. Sanzu isn't just annoying—he's dangerous. And he wouldn't hesitate to turn this entire ceremony into a disaster just to prove a point.

"Fuck you," you snap, barely keeping your voice steady.

Sanzu's smile fades, replaced by something colder, something far more dangerous. His eyes narrow, and for a brief moment, you wonder if you've pushed him too far. But then he chuckles, low and dark, like he's enjoying the tension between you.

"Feisty today, huh?" His voice is almost amused, but there's an edge to it, a warning. "You're out here sulking while your beloved plays house. Maybe that fairy tale you're clinging to doesn't mean shit anymore."

You feel your heart hammering in your chest, a mix of anger and something you can't quite place. It's the truth in his words that stings the most, the haunting possibility that he could be be right.

"At least I'm not the one standing out here with a stupid katana looking like a fucking fool," you shoot back, your voice sharp.

Sanzu's eyes flash, but instead of responding, he steps forward, closing the distance between you in an instant. His presence is suffocating, too close, too intense. You feel your pulse quicken, the air between you crackled with unspoken danger.

"Maybe," he murmurs, his voice low, almost a growl. "But you're not untouchable. Sooner or later, even Mikey won't be able to protect you. Then what?"

His words hang in the air like a threat, and for the first time, a shiver of uncertainty runs through you. You meet his gaze, refusing to show fear, but something about the way he's looking at you now—cold, calculating—makes your stomach churn.

You don't answer. Instead, you turn and walk away, your heels echoing in the empty hallway. But Sanzu's words linger, like a dark cloud that follows you, heavy and inescapable. You push them down, focusing on the only thing that matters: Mikey's promise.

But deep down, you wonder if Sanzu's right. And that thought, more than anything, terrifies you.

Manjiro Sano keeps his promises. At least, that's what you've always believed. He said it with conviction when you were fifteen, when his bright blonde hair caught the sunlight and his eyes reflected an unwavering certainty. His promises became your lifeline, a thread that tethered you to him, through the chaos of Tokyo Manji, through Bonten, through all the things that should have torn you apart. You never doubted him.

But now, with a ring on another woman's finger, that belief feels less like truth and more like denial. 

You lie beside him, his arms wrapped loosely around you, his breath steady against your skin. In the quiet darkness, you try to convince yourself that this—you—is still his reality. Not the woman he married out of obligation. Not the business empire he's running. But you, the one he promised forever. The one he swore to love no matter what. 

But there's something cold in his touch tonight. Not the soft warmth you used to know, but a distant, mechanical tenderness. His fingers trace absent patterns on your skin, but they feel foreign now, like they're just going through the motions. He's here, physically, but his mind is far away, lost in a place you can't reach.

"Did something happen?" you ask, keeping your voice light, even as anxiety twists in your stomach. 

He's staring at the ceiling, eyes vacant, as if the weight of the world is pressing down on his chest. The silence is thick, heavy, a barrier between you that wasn't there before. You wish he'd tell you. You wish he'd break through that wall and let you in, but he never does. Not anymore.

He shifts slightly, his eyes meeting yours for just a second. "What do you mean, love?" His voice is soft, casual, but there's something missing. Something that used to be there—a spark, a fire that you could always count on. Now, it's just... hollow.

"You seem distracted," you murmur, choosing your words carefully, even though your heart is screaming to ask more.

Mikey sighs, his chest rising and falling beneath you. He pulls you closer, but the embrace feels almost... polite. Like he's afraid to hold on too tightly. You want to shake him, to tell him to stop being so careful. To hold you like he used to—like he was afraid of losing you. But instead, he just holds you the way someone holds a fragile thing.

"Yeah," he admits, his voice quieter now, as though he's confessing something he doesn't want to. "It's just Bonten stuff."

And that's it. The conversation ends. Your heart clenches at the emptiness of his explanation, at how easily he can sweep your concerns under the rug. 

You know Bonten is complicated—dangerous even—but you've always been kept at a distance from that side of his world. He's never let you close enough to see the true depth of what he's carrying. You've respected his boundaries, trusted him, but now you wonder if that distance is starting to destroy you.

"Oh." The word leaves your lips, but it feels small, insignificant.

The silence returns, thicker than before, wrapping itself around both of you like a suffocating shroud. You stare at him, at the man you once thought you knew so completely, and wonder when he became a stranger.

You want to reach out, to bridge the gap, but fear holds you back. There's a fragility in the air tonight, something that makes you hesitate. If you push too hard, if you ask for too much, you're afraid the entire thing will shatter. Maybe it already has. Maybe that's why his touch feels different now, why his kisses lack the urgency they once had.

You long for the Mikey who would stay up with you until dawn, laughing, his arms tight around you as if you were his whole world. You miss the nights when he couldn't keep his hands off you, when his love felt raw and reckless, a fire that burned brighter than anything else. Now, it's all ashes.

"You don't have to carry it all alone," you whisper, hoping that your words might reach him, might bring him back from wherever he's gone. "I can help. You don't always have to protect me from it."

He doesn't respond right away. For a long moment, there's only the sound of his breathing, deep and rhythmic. When he finally speaks, his voice is distant, almost resigned.

"I know."

But he doesn't mean it. You can hear it in the way he says it—like it's just something he's supposed to say, not something he believes. His walls are still up, and you're on the outside, no matter how close you are in this bed, no matter how many nights you spend together.

You press your cheek against his chest, listening to the steady beat of his heart. Once, that sound would have comforted you. Now, it only makes you feel more alone. Even when he's with you, he's somewhere else. And the space between you grows wider every day.

"Mikey..." you try again, but your voice falters. 

You want to tell him you're scared. That you're afraid you're losing him, that this marriage is pulling him further away from you than you can bear. But the words won't come.

He presses a soft kiss to your forehead, but it feels like a goodbye more than a reassurance. And that scares you most of all.

You close your eyes, trying to drown out the doubts, the fear, the aching emptiness. But it lingers, like a shadow that won't go away. You tell yourself he still loves you. He promised you forever. He's just... distracted. It's Bonten. It's the marriage. It's everything else.

But deep down, you know. You know that the Mikey who promised you forever is slipping further and further away. And no matter how hard you try, you can't seem to pull him back.

Manjiro Sano never lies to you. He never has before, and you never thought he could. You know he keeps secrets sometimes, but it's always to protect you—or so you've convinced yourself. You've clung to this justification, repeating it like a prayer when things feel too uncertain. 

When there's a question he doesn't want to answer, he'll give you a vague response, the kind that leaves you in a haze of ambiguity, and you never push him further. You know better than to force the issue. Sometimes, he'll be blunt and tell you outright that it's none of your concern. But a lie? Never.

At least, he never did until now.

Sitting across from him, in the dim light of your shared apartment, the shadows cast across his face, you notice the subtle shift in his expression. His gaze remains low, unfocused, like he's avoiding you. The way his fingers tap against the armrest of his chair—once steady, now restless—betrays him. The quiet cadence of the room, punctuated by the tension building between you, only makes his discomfort more pronounced. 

You know he's lying, even though the words are barely out of his mouth. It feels like a crack splintering through the foundation of your entire relationship.

It's not that you're good at detecting lies; you've never needed to be, not with him. His cold distance has always been paired with an odd, unwavering honesty, no matter how painful it could be. But this time? This time, he's hiding something. His body language is too off, too tense, like he's barely holding onto his own façade.

You asked a simple question: "Where were you?"

He hasn't been home in a week. It's not unusual—Mikey has never been the type to stick around. You've long since accepted the lonely nights, the excuses of 'business meetings' and 'late-night operations' with Bonten. You'd even accepted the wife. 

But something feels different now, a gnawing unease that claws at the back of your mind. You thought he'd say he was dealing with Bonten's usual mayhem, or perhaps, reluctantly admit that he'd been spending time with her. Anything would've been better than the silence hanging in the air now, thick with unspoken truths.

But you never expected him to lie.

Instead of the rage you thought would surge, an icy dread curls through your chest. Fear. A raw, unsettling fear that digs its nails into you as you realize just how far away he feels. As if he's not just sitting across from you, but miles away, unreachable. The distance between you stretches and stretches, suffocating in its vastness. It's like watching him drift out to sea while you stand, helpless, on the shore.

You need answers. The kind you know Mikey won't give you. So you turn to the only other person who might know what's going on: Haruchiyo Sanzu.

God, you hate him. There's not a day that passes where you don't fantasize about knocking that arrogant smirk off his face. Sanzu embodies everything that repels you—his cruelty, his recklessness, his toxic devotion to Mikey. But one thing you can count on is that Sanzu never spares your feelings. If anything, he takes sadistic pleasure in tearing you down with his cold truths. 

And that's why you're standing here, in front of his door, hand trembling slightly as you press the doorbell. The silence stretches, your heartbeat loud in your ears. You press the button again, your anxiety spiking with each passing second. 

Finally, the door creaks open, and there he is—Sanzu. He leans lazily against the doorframe, like your presence is a personal offense. His disheveled appearance surprises you—hair unkempt, shirt unbuttoned at the top. There's a faint scent of soap, but he looks like he's been in a rush, as if your arrival interrupted something.

His eyes narrow, flashing with irritation. "The fuck are you doing here?" His voice is cold, almost bored, like he can't be bothered to care.

"I need to talk to you." You're surprised your voice comes out steady when everything inside you feels like it's spiraling out of control.

Sanzu doesn't even give you the courtesy of a full response. He turns, slamming the door behind him, heading toward the elevator without a second glance. You follow, your pulse quickening. His long strides make it difficult to keep up.

"Where are you going?" you ask, slightly breathless. You hate how small you feel next to him, like you're always scrambling to catch up.

"To work. Where else?" He doesn't even look back as he taps the elevator button impatiently. His eyes flick to you briefly, condescending, before he adds, "Unlike you, I don't have the luxury of doing nothing all day."

The dismissiveness in his tone grates on your nerves. You swallow back the retort, knowing it's not worth the fight. You're not here to argue with Sanzu—you're here for something much more important.

The elevator ride is thick with tension, the air suffocating between you. He stares at the floor numbers as they change, clearly eager to get away from you. You take a deep breath, summoning the courage to say what you came here for.

"I need to ask you about Bonten." Your words feel heavy in the silence.

Sanzu's head snaps toward you, eyes sharp and piercing. There's a moment of silence, and you feel the weight of his stare, like he's assessing how much to toy with you before answering.

"I warned you," he says, voice dangerously low. "Stop sticking your nose where it doesn't belong. Just because you're Mikey's little sidepiece doesn't mean you're part of this world."

Sidepiece. The word hits like a slap, stinging far more than you'd care to admit. But you hold your ground, your voice sharper now as you bite back, "I was asking nicely, wasn't I?"

He lets out a cruel chuckle, his amusement laced with mockery. "And you should've known better than to come to me."

When the elevator doors open, Sanzu strides out, leaving you to catch up once again. You hurry behind him, the cold concrete of the basement parking lot biting through your shoes as you watch him head toward the row of parked bikes.

"Just tell me where Mikey's been," you call out, your voice cracking slightly. The desperation seeps through despite your best efforts to keep it buried. 

Sanzu doesn't even slow down. He throws a leg over his black superbike, adjusting the helmet in his hands. 

His tone is icy as he responds, "Why the hell would I tell you?"

You feel the panic rising, the gnawing insecurity clawing at your chest. You can't let this go. 

"It's his wife, isn't it? Something's going on between them?" The words tumble out before you can stop them, but you know it's true.

Sanzu finally turns to face you, his expression dark, a twisted glint in his eyes. "You really wanna know?" His voice is like a knife, cold and cutting. 

"Married couples fuck and have kids. You didn't think they'd just sit around holding hands, did you?"

Your world tilts. Pregnant. Mikey's wife is pregnant. The words hang in the air, crushing you. Sanzu's bike roars to life, drowning out everything as he speeds away, leaving you standing there, reeling.

Manjiro Sano says he still loves you. He says it so many times, even when you confront him about her pregnancy. You have tears in your eyes, your voice quivering as the words left your lips. His hands, warm and gentle, hold you close—just like always. The softness in his embrace feels too familiar, almost comforting, like you could convince yourself, just for a moment, that nothing has changed. That you could still believe him.

He'd whispers that she might be his wife, but you are the one who had his heart. That his feelings for you haven't shifted, not even after this new life he is bringing into the world. That you still matter.

But something about it never sits right after that day.

It isn't the sex that bothers you. You've made peace with that. He is married, after all, and while it stings, you tell yourself it's just physical. Something they have to do. Something that won't affect your place in his life. Mikey's quiet assurances of love are enough to quell the hurt, at least for a while. He always knows exactly what to say, how to soothe your insecurities without letting them fester.

Until they do.

Each time he doesn't come home, doesn't call, doesn't text—each time he leaves you waiting, that old promise of his love grows weaker. It starts to feel like a distant echo, hollow and fragile. The uncertainty eats you away, the creeping doubt filling the space between your conversations. And then comes the guilt. You couldn't ignore it anymore, couldn't shove it to the back of your mind. She is pregnant with his child. 

And you? 

You are the other woman now. The mistress. The sidepiece. 

You tell yourself to be patient, to wait it out, to trust him. But those same reassurances you cling to begin unraveling with every unanswered phone call. Mikey's silences cut deeper than his words ever could, a painful reminder that you are no longer the center of his world. You are becoming the afterthought.

And today is your ninth anniversary. Nine years.

Nine years since the day the two of you had become inseparable, since the day you thought you'd be each other's forever. And as you get ready, as you slip on your favorite dress and touch up your makeup, you're hit with an overwhelming sense of nostalgia—memories flooding back of how you used to be. How easy it was back then, how natural everything felt when there were no lies between you. 

It takes everything in you to keep your spirits up as you head to his office, imagining the look on his face when you surprise him. Maybe that's what you need—a face-to-face reminder of who you are to him. That spark between you will rekindle, and the distance will melt away.

You hope.

The lobby feels colder than usual, and as you step inside, something feels off. The receptionist greets you with a stiff smile. You've seen her enough times to know that she's never this tense. She doesn't say much, but there's an awkwardness in the air, like she knows something you don't.

Your nerves tighten as you enter the elevator. The ride to the top floor feels longer than usual, the anticipation in your chest growing with each passing second. When the doors open, you step out into the executive lounge, the familiar sight of Bonten's most trusted members lounging around.

Ran is the first to notice you, his lazy smirk never quite reaching his eyes. Kakucho is next, nearly spilling his drink when he spots you.

"You okay there?" you ask with a light laugh, trying to ignore the unease in the pit of your stomach.

Kakucho straightens up, but his eyes dart nervously toward the hallway that leads to Mikey's office. "You here to see Mikey?" he asks, his voice strained.

You nod, offering him a small smile. "Yeah. I thought I'd surprise him." 

Ran's smirk doesn't falter, but there's something about the way he's watching you that makes your skin prickle. 

"Surprise, huh?" he says, his voice cool and detached.

Kakucho shifts uncomfortably, his gaze flickering between you and the hallway again. "Maybe now isn't the best time..." he starts, his voice trailing off as if he doesn't want to finish the thought.

But you brush off the strange tension between them. Kakucho's always been awkward with you, right? 

You make your way down the hall, your heels clicking against the marble floors in rhythm with your racing heart. This is supposed to be a happy moment—your anniversary. You don't want to ruin it by reading too much into their strange behavior.

But then you hear it.

A voice. Her voice.

You freeze mid-step, the sound of her moaning his name sending a violent shock through your system. The world around you blurs, your body moving on autopilot as you edge closer to the door, your hand trembling as you press it against the wood. The crack in the door is just wide enough for you to see.

Mikey is there, his wife's legs draped over his shoulders, his hands on her thighs, his face pressed between her legs.

You can't breathe. 

This is different.

Not the act itself—but the intimacy, the tenderness in how he touches her. He's doing something for her that he's never done for you. Not once, in all your time together, had he ever gone down on you. But here he is, giving her something more, something deeper. And you feel your heart shatter into a million pieces.

You can't stay here.

Your feet carry you backward, your movements slow, cautious. You shut the door as softly as you can, careful not to make a sound. Your entire body feels numb, a sick feeling twisting in your stomach as you stand there, staring at the ground, trying to process what you've just seen. 

Why did he never do that for you?

A rush of shame washes over you, mingling with the rage bubbling in your chest. You'd always told yourself you were enough for him. But now you wonder—were you? Was it all a lie, just something to keep you hanging on, while he gave her all the things you thought were reserved for you?

The world feels like it's tilting around you, the walls closing in as you stand there, numb. The sound of footsteps snaps you back to reality.

"You're here to see Mikey too?" Kakucho's voice filters through the haze.

"Yeah, yeah," comes the lazy reply. 

It's Sanzu, his voice slurred and casual, as if nothing in the world could touch him. He's closer now, and you barely register it, lost in the whirlwind of your own thoughts.

Ran's voice follows, a teasing edge to his tone. "Dude, you're tripping balls."

Sanzu laughs, a sound so careless it makes your skin crawl. "Friday night, what'd you expect?"

Before you can fully process the situation, a rough hand grabs you by the arm and yanks you back. You stumble, whirling around to face him.

Sanzu.

His teal eyes are wild, bloodshot and blown wide from whatever cocktail of drugs he's taken today. You know he's high, as the smell of drugs clinging to him, intoxicating the air around you.

"What the fuck are you up to this time?" he sneers, his voice low and mocking.

You try to pull away, but his grip tightens, his fingers digging painfully into your arm. "S-Sanzu, I—"

He cuts you off, his face uncomfortably close to yours now. "Scared?" he murmurs, his breath hot against your skin. The sick amusement in his voice makes your stomach turn. He's enjoying this—enjoying your fear, your vulnerability.

You try to twist free, but he pulls you closer, his lips curling into a twisted smile. "You should be," he whispers, his voice dripping with malice.

Your heart races, panic clawing at your chest. Sanzu when he's like this—high, unpredictable—is a beast you've learned to fear. He's always been unstable, but now, he's downright terrifying.

Yet, as you stand there, trembling in his grasp, all you can think about is Mikey. The lie he told you. The image of him with her, of how easily he discarded you, flashes through your mind again and again.

I still love you.

The words are poison now, burning through you as Sanzu's grip tightens.

< part one ends >

author's notes. heyy sanzu kinnies <3 i'm so excited to finally share the first part of 'bonten's number two'!! this idea has been brewing in my head for two years lol and i cant wait to see what you think ;) if you enjoyed it, please consider leaving notes! i'd love to hear your thoughts!! thanks for reading guys! you're awesome (๑˃̵ᴗ˂̵)و

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