Karamatsu X Ichimatsu

Honestly, this pairing feels like a niche inside a niche, but that's where some of the most interesting character work happens. 'Karamatsu x Ichimatsu' isn't about the obvious clash of the 'cool' brother and the 'gloomy' brother; it's about the shared, suffocating experience of being the middle children in that chaotic family. Karamatsu's desperate, performative need for love and Ichimatsu's cynical, withdrawn rejection of it are two sides of the same coin—they both feel unseen, just coping in opposite, disastrous ways. I've seen fics that frame their dynamic as a twisted mutual understanding, where Ichimatsu is the only one who sees through Karamatsu's act, not to mock him but because he recognizes the fakeness as a familiar defense mechanism. The angsty potential is off the charts.

Most of the fics I've found lean heavily into the angst-to-comfort spectrum. There's one called 'Static and Stage Lights' that stuck with me, where they'd meet on the rooftop at night, Ichimatsu feeding stray cats and Karamatsu practicing his painful guitar solos, and they just wouldn't talk. The tension was in the silence and the unspoken agreement not to perform for each other. It wasn't romantic so much as desperately needed companionship. Other writers go for more crack-treated-seriously premises, like exploring what would happen if Ichimatsu actually believed one of Karamatsu's delusional pick-up lines, leading to a bizarre, awkward courtship. The ship really thrives on authors who are willing to sit in the discomfort of their personalities instead of smoothing them over.

You have to dig through a lot of other, more popular pairings to find them, but the search is worth it for those moments of raw character study. I sometimes find better stuff under the 'Matsuno Brothers' or 'Platonic & Romantic' tags than just the direct ship tag, since their relationship is so layered it defies easy categorization. The fics that work best, for me, are the ones where neither character is 'fixed' by the other; they just find a strange, grating harmony.

so I feel this question in my bones. Finding emotionally deep fics for Karamatsu and Ichimatsu specifically is a bit of a niche hunt, even within a huge fandom. A lot of fanworks can lean into the absurd comedy of the source material, but the brothers' dynamic has so much potential for melancholy and quiet connection.

My absolute top recommendation would be to use AO3's filtering system to its fullest. Tag the pairing as 'Karamatsu/Ichimatsu Matsuno' and then sort by kudos or bookmarks. That's where the community-vetted gems usually float. But the real trick is adding additional tags in the 'Search within results' box. Try 'Angst', 'Emotional Hurt/Comfort', 'Character Study', or 'Pining'. I've found some astonishingly quiet, introspective stories that way, where the focus is less on romance and more on two deeply lonely people finding a fragile understanding.

Don't sleep on fanfiction.net either, even though it's older. Some of the most hauntingly beautiful KarmIchi fics I've read are from 2016-2017, when the show's first season was fresh and writers were really digging into the characters' insecurities. The search function is worse, so you might have to wade through more fluff or crack, but it's worth it. I still reread one from there about them sharing a cigarette on the roof in the rain; it had almost no dialogue but captured that shared, heavy feeling perfectly.

The pairing really thrives on subtext, so the best fics often mirror that with a slow, internal pace. Sometimes you have to read between the lines of a longer ensemble fic where their relationship is a subplot. It feels fitting, honestly, for two characters who aren't great at talking about their feelings.

This pairing thrives on a really specific kind of angst, honestly. Most fics I've seen zero in on their shared self-loathing, but twist it so they're the only ones who can see through the other's act. Karamatsu puts on this flashy, 'cool' persona, and Ichimatsu is the grumpy cynic, but the stories love having them acknowledge how hollow those facades feel. They're both fundamentally sad guys who think they're unlovable, so the romance often comes from a place of 'if no one else will have us, we'll just have each other.' It's less about grand passion and more about two people finding a quiet, grimy corner of the world where they don't have to perform.

You also get a lot of caretaking tropes, but it's weirdly reciprocal. Ichimatsu's the one dragging a sick Karamatsu home, but Karamatsu's the one who remembers to feed the stray cats when Ichimatsu's in a depressive slump. The physicality is interesting too—it's rarely described as traditionally romantic. More like exhausted leaning, or sleeping back-to-back for warmth, or Ichimatsu tolerating Karamatsu's terrible fashion choices as a weird form of intimacy. The setting details matter: a lot of scenes happen in their shared bedroom, on the roof, or in dimly lit alleys, which fits their need to escape the overwhelming energy of their other brothers. The conflict is usually internal, battling their own worthlessness, rather than some external villain. It makes for a slow, quiet, and often bittersweet read that just fits their dynamic perfectly.

I’ve noticed a shift over the years in what works for Karamatsu and Ichimatsu fics. The classic 'enemies to lovers' arc gets thrown around a lot, but it often feels forced for them—they’re not enemies, really, more like two weird puzzle pieces that don’t know how to fit. I keep coming back to the 'fake dating' trope, honestly. It sounds cheesy, but imagine Ichimatsu, socially anxious and miserable, somehow agreeing to pretend-date his flashy brother to get their mom off their backs. The inherent tension between Karamatsu’s performative affection and Ichimatsu’s reluctant, grumbling participation writes itself. The best ones I’ve read use it as a cover for exploring their shared insecurities; Karamatsu hiding his loneliness behind the act, Ichimatsu slowly realizing the attention isn’t so bad when it’s from someone who actually gets his brand of misery.

Another underrated angle is the 'caretaker' dynamic, but flipped. Everyone expects Ichimatsu to be the one needing care, but what about Karamatsu breaking down? A story where his constant peacocking finally leads to a massive burnout or injury, and the only person who doesn’t find it annoying or pitiable is Ichimatsu, because he recognizes that particular flavor of exhaustion. Ichimatsu’s quiet, non-verbal way of providing care—just sitting in the same room, handing him a cup of tea without a word—fits so much better than grandiose gestures. It strips away the layers and leaves the raw understanding between them.

I’m less convinced by the high-concept AUs for them, like fantasy or superhero settings. The magic is in the mundane, cramped space of their bedroom and the weight of all their unsaid history. A simple 'roommates moving out' scenario, where they’re the last two left in the Matsuno house, can be more explosive than any epic plot.

Honestly, tracking down the 'highest-rated' stuff for that pairing is a weirdly specific quest. AO3 is the obvious big one, no question. Their kudos system is basically the fandom's universal like button, and searching by Karamatsu/Ichimatsu and then sorting by kudos will give you the community-approved hits. I've seen some absolutely devastating angst pieces there that have thousands of kudos; people really respond to the darker, co-dependent potential in that dynamic.

But I feel like FF.net gets unfairly slept on for Osomatsu-san fic sometimes. The lack of a proper tagging system means discovery is tougher, but if you dig through the 'Osomatsu-san' category and filter for the pairing, the stories that do surface often have massive, loyal followings from the older guard of the fandom. The reviews can be way more passionate and detailed than a simple kudo. The rating system is less granular, sure, but a story with 500+ reviews on FF.net carries a different weight of community engagement, you know? My personal favourite, 'Solace in Blue', is on there and it's got this quiet, melancholy vibe you don't always see in the more trope-driven stuff on AO3.

Don't even get me started on Tumblr. The 'best' fics aren't always the most kudo'd or reviewed; sometimes they're the ones that get passed around in reblog chains with hundreds of 'OH NO MY HEART' tags. Finding those is a true deep dive into the tag and hoping someone has bookmarked the masterpost.

The dynamic between Karamatsu and Ichimatsu in fanfiction often centers on a powerful push-and-pull born from their starkly different expressions of the same core loneliness. Karamatsu's performative, outwardly affectionate 'cool guy' persona constantly clashes with Ichimatsu's cynical, withdrawn, and self-deprecating nature. A pervasive emotional conflict is the raw frustration each brother feels toward the other's perceived inadequacies: Ichimatsu is infuriated by Karamatsu's perceived insincerity and need for validation, viewing it as a pathetic facade, while Karamatsu is hurt and bewildered by Ichimatsu's relentless rejection and harsh insults. This creates a cycle where attempts at connection, often clumsy from Karamatsu or begrudging from Ichimatsu, are met with deflection, deepening the isolation they both secretly feel.

Many stories delve into the idea of seeing through the other's act, which becomes its own intense conflict. Ichimatsu might slowly perceive the genuine, awkward vulnerability beneath Karamatsu's shiny jacket and borrowed phrases, but acknowledging it feels dangerous—it means caring, and caring opens him up to immense hurt. Conversely, Karamatsu might begin to interpret Ichimatsu's insults and grumbles not as pure contempt, but as a twisted, familiar form of engagement, the only language Ichimatsu knows for intimacy. The emotional turmoil then shifts to the terror of changing their established, dysfunctional dynamic. If they stop fighting, what are they? If Karamatsu drops the act, does he have any worth? If Ichimatsu accepts kindness, does he deserve it?

A very specific and poignant conflict explores the tension between disgust and desire, often filtered through issues of self-loathing. Ichimatsu, who frequently expresses disgust for himself and the world, might project that onto Karamatsu, yet find himself drawn to that very same source of light he claims to despise. This can manifest in narratives where physical or emotional closeness is followed immediately by a vicious verbal retreat, leaving both characters reeling. Karamatsu's conflict is mirrored; his desire for love and admiration clashes with his internal belief that he is, as his brothers often imply, fundamentally lame and unlovable. He might seek solace in Ichimatsu, the one who vocalizes these insecurities most brutally, in a painful form of self-flagellation that blurs into desperate affection. The resolution, when it comes, is rarely a grand romantic declaration, but a quiet, shared understanding of their mutual brokenness, a tentative agreement to just exist together without the performative layers, which in itself is a monumental emotional shift for both.

Man, that's a pairing I've thought about a lot, but rarely see people discuss the rivalry angle head-on. Most fics I've stumbled into sort of gloss over it, leaning hard into the angst of unrequited feelings or the secret sweetness under Ichimatsu's grumpiness. But when someone does tackle the rivalry, it gets fascinatingly messy. They're both middle children, right? Karamatsu's desperate for recognition and Ichimatsu's content to be overlooked, but they're clashing for the same emotional space—neither feels seen by the family, but in opposite ways. I read one where Karamatsu's flamboyant 'painful' acts were reimagined as a direct provocation aimed solely at Ichimatsu, to get any reaction out of him, even contempt, because indifference was worse. That flipped the script for me. The rivalry isn't about winning; it's about forcing a connection, however toxic.

It also gets intertwined with their self-loathing, which is a huge part of their characters. In a lot of fics, their rivalry is a mirror—they see the worst parts of themselves in each other. Karamatsu sees Ichimatsu's depressive realism as a judgment on his own hollow performance, and Ichimatsu sees Karamatsu's desperate need for love as a pathetic version of his own hidden desires. The conflict becomes this cycle of pushing each other away because getting closer would mean admitting those similarities. I've seen it played for dark comedy, with them one-upping each other in melodramatic misery, and for genuine hurt, where their arguments dig up every buried insecurity. The best portrayals don't resolve it neatly with romance; the rivalry simmers underneath, adding a bitter edge to any tenderness that makes the whole dynamic feel dangerously real.

The dynamic between Karamatsu and Ichimatsu in fanfiction rarely just rehashes the straightforward sibling bickering from 'Osomatsu-san'. What hooks me is how writers use that established rivalry as a raw material to build something way more intricate. I've seen a ton of fics where the rivalry isn't the end point—it's the catalyst. It morphs from petty insults and silent treatments into this intense, almost obsessive form of attention. Ichimatsu's dismissals become a language of their own, a way to engage that's safer than admitting any kind of need. Karamatsu's flamboyant suffering is a performance aimed squarely at one brother who he knows is actually watching. The conflict becomes the only conduit they have for any real emotion.

You see this handled in a few recurring patterns. There's the 'enemies-to-lovers' pipeline, sure, but more often it's a 'rivals-to-reluctant-caretakers' scenario. Ichimatsu finds one of Karamatsu's tacky glasses broken, and instead of mocking him, he secretly fixes it. Karamatsu overhears Ichimatsu defending him to one of the other brothers in his own gruff way. The rivalry provides the perfect cover for these tiny, charged moments of vulnerability. It lets them maintain their dysfunctional personas while the story quietly dismantles them. The best fics make you realize their fighting was never really about hatred; it was a messed-up, constant dialogue, and fanfiction just translates that dialogue into something resembling affection, however grudging it might be.

It's less about who wins the rivalry and more about how the space between them gradually shifts from a battleground into something almost intimate, often without either of them acknowledging it out loud. The tension doesn't dissolve; it just changes flavor.

Okay, so there's a treasure trove out there, but the ones that stick with me are the slow burns that really get into the logistics of their arrangement. There's this one on Archive of Our Own, 'Terms of Engagement,' that nails the bureaucratic nightmare of two hyper-competent people trying to navigate a fake marriage for a mission. The author spends pages on them arguing about furniture procurement forms and weapon-cleaning schedules, and it's weirdly the most romantic thing ever. You see the trust building in the margins of their mission reports.

It completely skips over the usual 'oh no we have to share a bed' tropes and instead focuses on the quiet moments—Irina meticulously choosing a perfume that won't interfere with Karasuma's situational awareness, or him adjusting his running route so he 'coincidentally' passes her favorite pastry shop. The romance is in the operational efficiency. The ending is just them sitting in silence after a debrief, and he wordlessly pushes a cup of tea toward her. No grand confession, but you know.

Other than that, I'd check out 'Conditional Cover' on FFN for a more action-heavy take, and 'Non-Standard Protocol' if you like a dash of humor where Irina tries to 'educate' the students on international relations as a cover.

Honestly, most fics make Irina too one-dimensional—just the seductress—but the good ones explore her professional pride clashing with her growing, very real frustration that Karasuma is the one person her methods can't read.

Irina Jelavić and Tadaomi Karasuma from 'Assassination Classroom' are such a weirdly compelling pair in fanworks because their dynamic is basically a template for the 'reluctant allies to lovers' trope, but with a military-grade twist. Irina's whole femme fatale shtick clashes perfectly with Karasuma's hyper-competent, deadpan stoicism. The funniest fics I've read lean into the absurdity of them being forced to work together as teachers—her trying to seduce him for intel, him treating her like another piece of malfunctioning equipment. It's hilarious, but then you get the fics that dig deeper, wondering what happens when the mission is over. Does she ever drop the act? Would he ever admit he finds her exasperating charm... charming?

The best explorations I've seen focus on trust, or the painful, slow construction of it. Irina's entire identity is performative; Karasuma's is utilitarian. So a good fic starts dismantling that. Maybe a mission goes wrong and he has to rely on her skillset, not just see her as a nuisance. Maybe she lets a genuine emotion slip and he's the only one who notices because he's trained to observe everything. That shift from seeing each other as tools or obstacles to seeing each other as people is where the real story lives. It's less about grand romance and more about two incredibly damaged professionals figuring out there's a person under the professional facade, which honestly feels more intimate than a thousand candlelit dinners.

I stumbled on a crossover once where they were both retired, running a bar together in some neutral city, and the whole thing was just them bickering over inventory while communicating in coded gestures, constantly scanning the room. It was a quiet, brilliant take on how their past would never leave them, but could become a shared language instead of a barrier. That's the kind of thing I keep going back for.