Does yamada know about reason akane and her ex before?
Yes
He does that unconsciously though, to be fair. As he said, he doesn't even remember that alex is a girl, he doesn't consider her a girl at all. Also she had a boyfriend and all maybe made him forget even further about being cautious. And he also immediately went to apologize too. Akane also knows that seems to be her problem where she got "overly" jealous over someone that she didn't need to worry about.
Agreeeed.. idk how you can forget so easily what Akane went through and then he didn't give her the space to process it.
F*ckin tired of someone who already knows what happened in the past yet doing it again and carelessly hurting them. Girl already have a past where his ex bf got stolen by a girl that he keeps talkin in an online game duh. Imagine the pain you will feel if you feel that it might happen again