It's most likely reincarnated, or like have a second chance of love, to love Sejin the way he should have in his past life. Which probably why he knows him so well.
Base on the clues, Sejin was his French "teacher", Uke treated him well up to certain points(or always), hence why Ido said he had always be kind at the beginning. Maybe he don't trust him in entirely which is why Ido think he was seducing him to obtain something or just have ulterior motives in his past life.
Probably purposely put it out there for him to see if he steal or not in this current life.
Bruh, Ido is a strange one. He knows Uke so damn well, it's creeping me out but he's so supportive and gentle
If Uke steals from him, I don't blame him. It's not easy to recover from abuse and manipulation