This is a difficult question for various reasons. I’ll say for now I’d like people to try thegrimzuera’s How We Learn to Love if they haven’t yet. It’s a (community) college AU set in the US so I know it’s not for everyone, but the writer puts a lot of thought into both Bakugou’s and Kirishima’s growth as characters. Personally I’m a big fan of her showing how Katsuki’s anger is also a positive trait of his. We’re shown a lot of how and why they are the way they are actually. Katsuki’s issues with his mother will stab at your heart in the way you want fic to hit you (Mitsuki is not a good person in this, be aware). Also mind the rating and tags of course.