Having bore witness to the height of the KH craze back in the 2000s, I can say many weebs would "cosplay" as their own Org XIII OCs (guys in the black coats).
The crux of these characters, as someone pointed out earlier, were soul-less edgy emo doppelgangers of other characters. Requirements to be this type of character for your OC? Wear the jacket, be depressed, and add an X to your name when rearranged.
So maybe Adam isn't "cosplaying" as Roxas (who he will eventually based on his purchase history) but his own OC. Name possibilities include:
XADAM
MADAX
DAMAX
Probably DAMAX since it's close to an actual character, DEMYX. Maybe that's why he chose that moniker all those years ago...