The problem with this idea is that they've already confirmed he's not the original in conversations among themselves that he wouldn't be aware of.My theory is that he is golden man and this is all some scheme they've concocted with the original golden man personality so they can draw out and take down the dark side. He erased his own memory and changed his appearance and they're all going along with it so that they can fool the dark side villains.
Feels a little too simple but it seems to be the easiest plot. I actually hope it doesn't go that way tbh.
Oiran knew him as kid, so that's highly unlikely, when they fought we've seen a supposedly him as kid and she was about to say his nameOk, got it. Golden Man is a clone, and the main character is the Second Clone.