The difference between "I love you" and "I'm in Love With You" is that only one sounds like an apology.
Atsumu knows everything he needs to about love.
He knows love in the way his mother kisses his temple before he goes to sleep and the cool feeling of a volleyball under his fingertips.
He knows of love weaved intricately into the normalities of life, love like a routine. Atsumu never takes advantage of this tender love, instead reciprocating it in his own tosses and actions.
Atsumu's love has never required talking, so he doesn't quite understand it when Osamu whispers to him a quiet, "I still love ya." His words are soft and tender, spoken like a promise.
It is the first (but far from the last) time that Osamu has missed a set from his brother. Perhaps out of habit, Atsumu lashes out at him and expects Osamu, out of habit, to lash back. But instead, he's met with quiet resignation, the huff of breath 'Samu always takes before he apologizes, and a gentle "I still love ya."
Atsumu isn't sure what prompts him to say it. He doesn't ask to find out.
It's a few years later when Osamu teaches him even more about love.
Between the two of them, they've said "I love you" enough times to count on one hand but the unspoken words are never missed in a trusting set or warm breakfast. Atsumu knew what it meant to love Osamu before he was even born.
But today Osamu doesn't say "I love you." Rather, his eyes are far away from Atsumu, tracing the smile of another teammate.
Atsumu follows his gaze. Suna is trying to stuff three of Osamu's homemade onigiri in his mouth. Atsumu starts to make a remark about how stupid he looks.
"I'm in love with him," Osamu breathes out quickly, jamming his sentence together like it's all one word.
In a matter of seconds, Atsumu becomes intimately aware of the difference between loving someone and being in love with someone. It is spelled out in Osamu's eyes, creasing at the corners, and the way his lips tug upward to make all his features soft.
Atsumu is staring at a stranger. A totally smitten, far too happy looking, stranger.
He could vomit from how sappy this all was.
But none of that mattered to Atsumu, really. Osamu could be in love with whoever he wanted. It didn't affect Atsumu, who taught himself love was something to be observed, rather than experienced. For him, love has never been personal.
Everyone at Inarizaki Academy liked Kita, that much was obvious. It was hard not to like him, really.
Kita is a package deal: handsome face, strong arms, good grades, captain of the volleyball team, connections to Miya Atsumu. Really, what else could you want? And sure, that was plenty enough reason to like him.
But none of that meant Atsumu was in love with him.
No, Atsumu was in love with Kita because he saw Atsumu and Osamu, not AtsumuandOsamu. Atsumu was in love with the man who'd tell him whenever he saw something that reminded him of Atsumu, like the wildflowers on his lawn or the soft ska music his grandmother played.
Falling in love with Kita was like breathing; it happened so naturally and seamlessly that Atsumu barely noticed.
Inevitably, he realizes. It came as a quiet revelation watching his brother poison his living once again with the presence of his boyfriend. Atsumu could be happy for him that Suna returned his feelings (and he was, truly), but it was easier to simply feel spite.
"What's got yer panties in a bunch?" Osamu teased. "Go get yer own man instead o' staring at me and mine."
Atsumu would, of course, because he couldn't bear to lose to 'Samu and seeing him so foolishly in love made him wonder how it would feel to be wrapped in the arms of his captain, warm and protected.
He confesses on a cool spring day, the breeze blowing through him. There are wildflowers nearby, and Atsumu thinks he can hear students chattering in the classroom above them. It's by all means a normal day, and he is quickly reminded that this world he's worshipped to be Kita's is just as much his own.
"I'm in love with you," Atsumu explains, but his voice is cold and clerical. He confesses like a doctor giving a medical diagnosis, awaiting a reaction.
When Kita says, "I love you," his voice all tender like he's made a grave mistake, Atsumu doesn't respond.
Atsumu doesn't know everything about love, but he knows enough to leave before Kita can say, "I'm sorry."
