Edit: I would like to add that this was a very typical all ages appropriate highschool shoujo type setting, pg or at worst pg13.

Probably about 10-ish years ago give or take, I read an anthology (I think, could be all the same author and same place just different characters each chapter) that focused on love letters. It took place in a highschool and had a rather distinctice art style. The first chapter had a tomboyish looking short haired girl that liked books and would exchange letters by putting them inside the pages of a book and the guy (who turned out to be a boy she didn’t get along with in class) did the same. Upon finding out she misunderstands and thinks he was just making fun, but they become a couple. Another chapter had a guy with darker skin and dreadlocked or afro-y hair (not sure which can’t remember super clearly) who would draw tattoos on himself and others with sharpie and the girl fell in love after a while might have thrown like a bunch of love letters or a bunch folded into paper planes or just one ripped up one off the roof after a misunderstanding he sees and bla bla bla they become a couple. Stuff like that. Those two stand the most clearly in my memory, but there were others. I believe there were 2 or 3 volumes, but I could be wrong on that point.

Also the art style was similar to Setsunai koi, koibumi biyori, and loveletter from..., but was not any of those.