I don't think Akihiko is wearing a modern school uniform. Those uniforms come from men's every day clothes since the 1800's (that's in the western side, like England and such places). Men's fashion just began to clearly evolve/change since the 1970's, before that, all men wore suits and those didn't change much since the end of the 1700's. Also, you can clearly see Akihiko wear similar clothes throughout the whole manga.
I wouldn't bet a jellybean on my knowledge of period fashion either.
hahaha I wouldn't expect anyone to now either, I'm just overly interested in it and wanted to share (and I don't even think all I said is 100% accurate)
it's cool how you even know that much about it though. Passion in any form is amazing. In all honesty, i can't even remember what I wore yesterday
Things to think about from chapter 1:
-a grave for the "Kobayashi" family, which is Akihiko's last name
-the smartphone Kazushige was using which means it's way in the future
-Akihiko wearing modern school uniform in the official colored page