I get it's mainly for fan service, but is there any actual reason for him to be doing this?
Sounds like they were fine just being released since they asked for it directly. He agreed. And now its a competition with seemingly massive stakes for no reason.
@JavelinJoe As you said it's mainly fanservice, but thing is, as it's mentioned in the chapter gaap wouldn't believe MC that he wouldn't mind setting girls free as he could have some ulterior motive. So MC think of a way, and thats the competition as it wouldn't be so suspicious. I assume they want to just let her win, but taking this manga genre into account it will go down the hill lul.
Ehhhh... This kind of plot development is throwing me off a little... And it's not line he doesn't have released demons that can testify on his behalf if she doesn't believe him. I know it's for fan service, but this direction feels unnecessary.