I didn't even realize I had this marked to read (can't be bothered to check when either but it was probably years ago). I finally came across it again and only noticed after I finished, but now I wish I'd read it sooner. I'm always a bit on the fence with relationships where one of the partners is in high school. I guess he must have been a senior because he's a college student in the extras and there's a line where he says they'd been together for a year. But I actually really like this.
Anyway, the story focus mostly on the MCs and their feelings. They start liking reach other and get together very quickly but for such a short story I wasn't exactly expecting a slow burn. There isn't a lot of outside conflict, and side characters don't play much of a role. I do wish we'd seen more. Like Yamada going to see Chihiro's mom (it's just announced that he told her and she was fine with it) we also see an extra of them together 9 years later, and I wish we saw Chihiro's siblings because there's a short extra where his little brother says he'll marry Yamada-san when he grows older so they can play together every day I wish we got to see them become a family, not just the two of them, but with Chihiro's family, too. Also wish we saw Chihiro coming out in college because there was a scene where he got worried since a friend kept asking him to join a mixer (I won't explain this, you know if you've read manga for a while what it is) then it turns out Yamada already told his friends he was dating a younger guy. But oh well, what we do see is surprisingly cute and mature for a story involving a high school love interest and an adult.
Yamada To Shounen