The Nerd-chan

Things Bandou remembers (through point purchases) about his mortal life.

-every interaction he had with shouhei, including things he was there to witness him doing
>pulling him out of a river to save him from drowning
>him entering a building and being surprised to see him
>him reaching out to shake someone's hand, fire erupting around him and a flame shaped mark appearing on his arm
>him attacking men with a pipe that was engulfed in flames
>him talking about how everyone would want to be a part of HOMRA - doesn't know what that is except that it's a group, since he also remembers yelling about the fire symbol meaning they are comrades
>him calling him san-chan all the time
>pizza delivery boy!
>working at a burger joint together
>all the things that make him petty at shouhei

so he knows others have the same flame mark. Knows through the game that izumo has it too, eric's is still unknown to him

pretty much has proof that the mark is related to the fire aura - both through remembering shouhei with it and knowing izumo can also wield fire

then there's a bunch of headcanon stuff about his childhood. mostly shouhei beating him at things and getting into trouble because he's an idiot. kissing saya-chan noooo! and then the whole thing with him sneaking over because he was upset about his family. shouhei leaving to go to another school.