@Hootanic
Yuuta assumes he can't convince her by means of words because he sounds like the monsters that raped Amane friends in the past. He thinks he will just remind her of that happening when he talks to her.
So it's not really a matter of his confidence, he just trying to read into Amane...
I doubt we will see much more fighting of the main him/herself anymore. It's like the white cat says, his/her place of destiny is as a manager, not as a fighter. If he would use his previous life experience in the ring directly it would be cheating.