What I wonder is only whether mc became a girl in time travel, if he was a girl before time travel in this time line, or if he possessed a third party girl after time travel and original man still lives.
I would expect there to be a high chance "he" could meet his other self if this were true time travel(hence the need for another identity to change the timeline). That said more often than not its just going to be a replacement. Whether the girl originally existed or not is 50/50.
Just a small correction : the boy said he will help him if he can, not gives him some of his power. Translated like this the meaning changes completely.