i quite like sunaosa where osamu is very aware of his feelings for rintarou. and he's pretty sure that rintarou feels the same. he's pretty sure that they're moving at the same pace but he never mentions it.
he spends all of high school getting to know him inside and out, good and bad, all of the little secrets and random dumb quirks that you only get to see when you like someone a little too much. rin gets to know osamu just the same and he's so happy to finally have a best friend. he spent his childhood moving between schools, towns, prefectures, parents, everything. but now he has osamu. and osamu’s not going anywhere.
they go to their classes together, they eat lunch together, they walk home together, they sneak out for late night convenience store runs together. they'll sit on the floor of the twins' bedroom and do homework together. osamu will make fun of rin's english and then help him with his vocabulary. rin will bitch about osamu's reading comprehension but quiz him on his kanji until he gets it right. they'll go up onto the rooftop late at night with ice cream and too many stories to tell. they'll lie down, a little too close to each other to just be friendly, and talk until osamu's yawning more than he's speaking. rin will call him an old man with his grey hair and early bedtime and osamu will threaten to push him off the roof. they'll climb back inside and squeeze together on the bottom bunk because they haven't pulled out the futon for rin since their first year.
they'll get closer and closer until they graduate and moving apart feels like losing a limb. osamu will keep quiet as his feelings grow and he'll wait for rin.
he'll wait for as long as he needs.