Nagi Seishiro Smut - Tumblr Posts

guys he's so fine and cute i can't, he gives so my man

nagi seishiro calls you mommy (fem & afab! reader)

18 + explicit, established relationship, breeding kink snuck in there, 1.8 k words

It starts off with you hating it.. he earns a scoff and a dry “I’m not your mother, seishiro nagi!” 

It’s a joke then. It turns light-hearted and mischievous, a tool for teasing since you really do fuss over Nagi in a way that feels…y’know…motherly. He won’t mention it if you aren’t in the right mood. The doting. The acts of service. The ooey-gooey love you weave into every one of your touches…

Truly, at first, it‘s only teasing. You’ve got a tolerance built for that already—your skin’s grown thick with Sei’s dubious filter and deadpan joke delivery. So when he senses you can handle it, the nickname gets repeated. 

A lazy “thanks mommy” falling from his lips when you hand him the phone charger he’d done an awful job searching for, swiping hair out of his face absentmindedly before you register his words. You pull your hand away fast when you do, groaning but giggling all the same. The following occurrence only earns a chuckle and a light shake of your head. The next time only a funny look. 

You must dwell on the new title more than you let on though, because inbetween Nagi’s chest and his comforter one night, you bring it up. 

Squeezing yourself as flush to his bare skin as possible, finger tracing his collarbone while your question comes in whisper: 

“So…why do you keep calling me mommy?” 

Seishiro’s half-asleep, so his answer comes out soft and heavy. “S’just how you act. And it’s pretty hot.” 

You scoff, rolling onto your back in a fit of defiance. You don’t think you act motherly.  Nagi’s quick to roll on top of you when you move, sticking to your chest like a magnet, clinging to your front and using your tits as a pillow—this position suits him just fine. 

Once he’s nuzzled in for maximum comfort he yawns. “Are you mad at me?” He lifts an eyelid to peek at your face. “Didn’t think it bothered you that much.” 

With a sigh your arms are around him, nails gently grazing his naked back the way you know he likes. 

“No, I'm not mad. Just feels weird. No one’s ever called me that before and when you do it I can never tell if you’re making fun of me.” 

He inhales a deep breath against your skin before he responds, lips dragging against your breast. 

“Not making fun. I really do think ‘t’s hot.” 

There’s a yawn and then a sleepy, open mouthed kiss on the soft skin above your nipple. 

“really?” 

“y’have no idea” 

There’s a few more drowsy kisses to your chest then, before your nipple’s latched into Nagi’s greedy mouth, the other circled gently with his thumb. You whine, running fingers through his hair and tugging at his roots. 

There’s a soft pop when he pulls away. 

“do you?” 

He squeezes your tits lazily in each palm while he asks, playing like they’re stress balls—such a regular occurrence it’s humorless by this point. 

“Do I what?”

“Think it’s hot? Mommy?” 

Your answer is a jagged sigh when he starts kissing his way around your other breast, glancing up to meet your gaze. 

“Umm. I’m not—“ 

His eyes droop closed and Seishiro moans a bit when your other nipple is captured between his lips. You feel him grind slow against your thigh then. 

Muffled: “Not?” 

“Not sure…” 

He pulls off of you then, looking at you with shockingly awake eyes for Seishiro Nagi past 10 pm on a weekday. 

“Well. D’you wanna test it? See if you like it?” 

You giggle. “How?”

He answers by crawling over your leg so his hips are slotted between your thighs. There’s a pause while he runs his signature vacant stare down your face before, without further segue, he meets your lips. 

You smile into his kiss, loving the familiar Seishiro-nature of it all. His kisses are always languid and effortless, comfortable and often somewhat lazy, but you like them best that way. They feel comforting. Just like all his late night touches, so vulnerable and safe and raw it’s heartfelt. 

This kiss takes little time to grow messy, licking inside each other’s mouths and eventually drooling till you’re needy and twitching around nothing, and Sei can’t seem to help but grind against your center. 

Your eyes fly open when he does; he’s so hard. 

Your lips separate then, catching your breath in ragged gulps of air while fingers run through Nagi’s hair, pulling bangs out of his face.  He only grinds his boxers deeper into you.

“You’re gonna fuck me?” 

Your voice is a whine while you lift your hips to meet his next movement, fingers clawing his back and his neck, careful not to dig nails in—classically gentle for him. 

“Can I?” His tone is desperate in a special rare way—one he reserves for your ears late at night—while he lets his forehead rest on the pillow above your ear, the next buck of his hips slower and deeper. 

You nod frantically, ripping down your panties before helping him tug at his boxers. 

No time is wasted—it feels needy and rushed when Nagi sinks himself inside not a second later. You find yourself clinging onto his arms for support—he’s normally slower, a bit more careful with you since he’s so big, but it’s like he’s forgotten his size when he shoves past your entrance, gripping the flesh of your hip like a lifeline till he’s bottomed out. It's a good thing you’ve been dripping with anticipation for a while now.

There’s a beat of stillness when he does, silent except for shaky breaths, where you each do nothing but adjust. 

Then Nagi is bending to his elbows, reaching an arm behind your back to snuggle himself close before fucking into you like he’s possessed. 

There’s barely any build up before he’s moving like there’s lives on the line, rolling his hips hard and deep and moaning in your ear all the while. 

You wanna tell him it’s too much but the most you can manage is an “Ah- Sei—“ before he’s squeezing one of your thighs up, reaching a new angle that has your words replaced with gasps. 

He smears a kiss by your ear before answering in a whiny pant, “yes, mommy?” 

Your closed eyes snap open at that, feeling fresh heat bloom in your tummy. Oh. 

Your body starts grinding up to meet his hips without thinking while your arms wrap around Seishiro’s back, rubbing sloppy circles into his skin while he continues to absolutely ruin your pussy.

“You’re—“ you wrap the leg he was holding around him, “doing so-ngh good Sei.”

“Yeah? Doing good f’r you?” He pants, hopeful and boyish and cute. 

You can only nod, squeezing him tighter with your leg as you approach your peak, Nagi clearly not far behind you as he drops his forehead to the pillow above your ear again, hugging you closer while somehow still fucking into you with the same frantic precision. 

“‘Am I—nggh ‘m I a good boy then?” You clamp down at his words, earning a hiss.

“Y-your good boy?” He adds, almost whimpers.

“Uh-huh… You’re my- hah- good boy Sei.” 

You cum then, making a high pitch noise at the relief of it, feeling Nagi fill you up a moment after. He doesn’t stop moving till you’re sensitive and sticky and full, his weight falling onto you in a heavy blanket once he’s done. 

A lot of the time now is when Nagi’s eyes droop too much for anything further, he’s chronically sleepy after all. But when his face lifts to see yours, his expression is very much conscious. and adoring. 

“Mmm Nagi?” You murmur his name like a caress, sweet as you can manage while pushing hair from his eyes for the millionth time. 

“Mhm?” 

“Want me to ride you?” 

He nods fast. 

By the time you’ve switched places and you’re easing down onto him, Nagi is starting to yawn again a little. His head is resting against the headboard, he’s relaxed. Because this is routine—you ride him all the time and it’s comfortable.

But while it’ll always be comfortable when it comes to nagi—the sex feels different right now—extra tender somehow. Tender but also filthy because your new name is still in the back of your mind as you’re split open, thinking about Nagi being your good boy again. 

He is, of course, without trying. panting soft and pretty once you’re bouncing hips against him in earnest, warm hands squeezing at your sides to help guide you up and down. 

You kiss his temple when he does, asking “How’s it feel, sweet boy?”

You curl your center forwards then, earning a jagged moan while Nagi’s breath catches in his throat. 

“F-fuck- so good mommy. S’too good.” 

You’re rolling now more than bouncing, slowing down to prolong the impending creampie… you want this feeling to last. 

Your easier movements finally give nagi the potential for brain activity, letting him open his heavy eyelids to watch you work, running palms up to knead your tits. 

“Such a pretty mommy.” He adds almost idly, tugging your nipples and bucking his hips when you tighten around him. 

You can’t help but chuckle at his words, shy again somehow. 

Through a yawn he asks, “does the sweet boy get a kiss?” 

That makes you giggle even more before you’re leaning in, locking lips deep and sensual while Nagi starts to help guide you up and down his length again. Your mouths are quickly swapping spit and drooling as you find a rhythm that way, hitting a toe-curling sweet spot inside you over and over that has you crying out into Nagi’s mouth. He moves long fingers between you to lazily rub at your clit when he feels you’re getting close, thudding his head back against the headboard when you feel so good you can’t kiss him back anymore.

Soon you’re coming undone for the second time tonight around him, clamping down so tightly that nagi can’t help but cum with you, rolling the back of his head against the headboard with his eyes all scrunched, whines of ngh m-mommy as he does. You feel his hot cum fill you for the second time tonight then, pouring inside for even more than the first time it seems as you rub a soothing hand over Nagi’s chest and thumb over his cheek throughout. 

With our further ado there’s a collapse, both of you remaining snuggled together while you try and adjust so you’re laying the right direction on your bed. 

Yawning, your breathing finally begins to slow in his hold, pretty sure Sei’s already asleep. 

But then he moves, adjusting so you’re both on your sides while he spoons you, a big palm falling over your lower belly, rubbing it a bit. 

You try to sleep like that, but then you’re dwelling on the sticky mess that remains between your legs, and the spot that nagi keeps on rubbing beneath your belly button. Over your fucking womb. 

Your eyes shoot open.

“Wait- Sei— you’re not thinking of actually making me—?” 

You’re met with only a soft snore.