I think people are overreacting over Yoshida's offscreen moments with Denji. They weren't close friends and Yoshida always had ulterior motives with him, but in a school setting it's hard to not have some goofy and juveline moments from time to time.

I think we all had that one classmate that wasn't a friend of ours but you still had memories with him since you stuck together for a while, I think that's how it is here.