Responses
The family name is haga. So both Hajime and the black hair dude have haga as their last name and just people close to them would call them with their real name, not their family name. You call ur teacher with their last name too :)
THE LAST CHAPTERS CONFUSED ME i thought the guy w the black hair was tatsu or whatever the main guys name is cause they referred to him as “haga” and didn’t everyone refer to the main guy as haga too??? so i rhought they had broken up and i was so sad but i then i realized it was a whole nother person