Zenitsu understands, he really does.
Being an uneducated feral boy, Inosuke gets thrown off, confused and overwhelmed over the smallest, stupidest things. It’s really embarrassing. Not to mention how it makes their job at detecting a demon even harder, considering anyone who could know something about it is too scared to approach them with a screeching boar man by their side.
So, while they’re not obliged to do any of this, Tanjiro and Zenitsu have this nonverbal agreement that they’d do their best to teach Inosuke some basic human knowledge. Things like social cues, social customs, or human inventions they might encounter.
And it’s good, it works. Inosuke stops scaring the general public and stops embarrassing them whenever him and Tanjiro (mostly Tanjiro, if he’s being honest, but Zenitsu still tries) are talking to people in search of clues. They also become greater friends in the process, which is a development Zenitsu never fully expected. The feeling of belonging together, of being cared for and caring in return is a new thing, and it’s as exciting as it’s frightening. But it’s thoroughly appreciated. Their travels in between jobs is a lot more pleasant and fighting is less scary with them around. They got his back so many times…
Still, no amount of appreciation for his friends can still Zenitsu’s nerves when he walks in the room to find the mess he encounters.
“What are you two doing??? ”
They’ve been sharing a room at the Butterfly Estate for a few weeks now, painstakingly recovering from their latest injuries. They’re still too battered and frail to do any sort of stamina training with Aoi and the other girls, so they’re spending most of their time resting. Sometimes, the little girls will come to their room with a chess board or some books they sneaked from Shinobu’s collection. But most of their time is spent laying down, chatting to each other and staring at the ceiling.
And while Zenitsu enjoys it, the other two are getting stir-crazy. He gets it, he really does. But why? Why are they like this?
“We’re building a pillow fort!” Tanjiro beams in his direction as he ties clean sheets to his bed’s headboard.
“We’re making a fortress!” Inosuke announces at the same time, jumping in his bed like he doesn’t have one or two broken ribs and some open cuts. “And you can’t get into it!”
“Inosuke, don’t be like that. You can sit here with us if you want to, Zenitsu.”
“No, no! He doesn’t get to be in my fortress! He didn’t help at all!”
Zenitsu stares at the mess his companions had done. In the time he was out taking a relaxing bath, the two of them had stolen all the other bed’s pillows, including Zenitsu’s , to make said pillow fort. The walls consist of both their beds, two of the unused mattresses on the ground, all the pillows are shoved inside close to the wall and the whole thing is covered by a sheet ceiling.
While he stares, the two builders excitedly crawl inside. They don’t giggle outwardly, but Zenitsu can hear it, loud and clear.
While the three of them are friends, Tanjiro and Inosuke are something else . There’s a different softness to their sounds when they’re together. It’s affectionate and sweet, giddy with excitement, ever present in Zenitsu’s ears when he’s around them yet still comfortable. A pleasant and loving hum as the background of everything they ever do.
It’d be a delightful sound to hear if it didn’t swell his heart with sadness. If only those loving sounds were ever directed to him…
As if that’s not enough, their actions sing the same notes. They always lean closer to each other, how they’re always looking longingly at one another when the other isn’t looking, how friendly touches linger for a while longer. Anyone could see it. Zenitsu’s sure even the girls had noticed; at least the three ones have, from how they sit back and watch when the two lovebirds interact.
Yet, they remain unaware of what they’re feeling and what it means. It’s pitiful.
“I don’t wanna be in your pillow fort, I want my pillow so I can sleep!” Zenitsu stomps in his place. “Aaaah, what’s wrong with you two?! You can’t take someone else’s pillow without permission! You shouldn’t have taken any of these pillows in the first place! Aoi-chan’s gonna be even madder at us now!”
“Ahh, sorry, I should’ve asked first.” Tanjiro smiles sheepishly, picking at their pile of pillows. “And I don’t know which one of these is yours, now…”
“Doesn’t matter! Doesn’t matter!” Inosuke laughs as he throws himself on the pillows, almost squishing Tanjiro’s hands in the process. “It’s all ours now, Monjirou! Belongs in the fortress! Screw his pillows!”
“Ugh, you’re insufferable, Inosuke! You’re a terrible friend! Why do we even hang out?!” he’s tempted to say no one would marry him, but Zenitsu knows it’s a lie. Tanjiro sounds insufferably fond, despite Inosuke being a selfish bastard.
Zenitsu’s ready to go lay down pillow-less and cry to himself about his loneliness when he hears a slight tap on a mattress. He looks towards them again and they’re both staring at him intently. Their sound gets louder, stronger, and Tanjiro taps the empty space beside him on the mattress again.
“I don’t know about Inosuke, but I want to take a nap, too.” Tanjiro says and fakes a yawn, still staring intently at Zenitsu.
“I’ll be watching the door!” Inosuke proclaims, scooting closer to the pillow fort’s entrance and sitting there, fists ready. “If they show up, I’ll challenge them to battle! They’ll have to take me down if they want our fortress!” Tanjiro barely suppresses a chuckle.
“...” Zenitsu’s protest doesn’t make it out of his mouth when his heart jumps up to his throat. He stands there, fidgets nervously, not knowing what to do, what he wants to do.
Zenitsu crawls into the pillow fort in the end, his own thundering heartbeat mixing in with the pleasant hum of affection in the background. Inosuke crawls to Tanjiro’s other side shortly after.
He’s not entirely sure how his own sounds contribute to their already established harmony, but it fits nicely enough.
(The three of them sleep peacefully through the afternoon, until they’re woken up by Shinobu’s scary presence at their pillow fort’s door, asking “What is it that you three have in here?” in a fake sweet tone. They scramble quicker than they ever did before, bowing their apologies and rushing to pick up the sheets.)