romantically, platonically… it doesn’t matter. the point is:
bakugou has a note on his cellphone where he writes stuff he learned while tutoring kami, like “bring skittles to study sessions and let him have one for every question he answers. (3 if it was a hard one and the dickhead got it right)”, and ideas to help his improvement, for example “use the pomodore method next week and see how it goes”
katsuki makes him jelly when he’s sad and always wait for denki to go shower so he can put it on his desk.
+ if kaminari’s really upset about grades, baku also puts a post-it on his spoon with a “hidden” note to cheer him up, like “your shitty grades are becoming less shitty, no wonder you’re my best student congrats on me for doing miracles as a teacher.“
he got a pop it keychain for denki at last year’s secret santa to prevent him from losting his keys (it used to happen at least once a week) and it worked well, since he’s always searching for the fidget toy in his pocket
katsuki has an alarm on his cellphone for kami’s medicine to make sure that the boy takes it at the right time
bakugou doesn’t like to have people on his room, but as long as kaminari shows up at his door with a book in hands, it’s ok. (he usually stays silent until he finishes it, making small noises here an there, so is a day of comfortable silence for both)
is common sense that denki NEEDS physical contact, and katsuki’s form of dealing with it is telling him to get off while not making any effort to actually get him off
when they come back to the dorms after weekends, bakugou often brings him homemade food using “my mom forced me to bring it to you” as an excuse (he does the same to bakusquad and other few classmates)
when they go out, he always look for things kaminari may have forgotten before leaving a place, like a cellphone in the uber, a coat next to the chair he was sitten at mc donalds… you got the point