I can sorta see the foundation this manga's trying to build. Something like "The classroom can teach a kid only so much about life. If you've never put your pride on the line in a 3rd Strike set how much do you really know about yourself? How much do you really know about your classmate if you've never 1cc'd Metal Slug with them before?"
I just wish Yamai wasn't so ho-hum as a character. All the other kids have clear motivations for heading to the arcade. Mirai can die at any moment so she wants to go out button mashing. Katagiri hates her homelife so playing Night Warriors is her way of escaping. Yamai? His grandma keeps seeing weird shit and maybe ghosts took his soul which is why he's so emotionless? He wants to start being taken seriously or something so he's gonna have arcade gremlin Arisu transform him or some shit? Not a good enough motivation. Even "I want to be able to shut down Katagiri's smug lil face at will" would be a better character motivation. But there's still hope for him I think.