I think we saw something important here. This probably isn't the first time he's been thought of as a target of affection by a girl, he isn't drawn like a bad looking guy, so there must be something wrong. Doesn't seem like he's sexually into Lolicons specifically so maybe it's emotional. Also I think the girl was chosen to be 14 more so because a 19 year old wouldn't work for this story, they could leave their home on their own. It only works if she's 14/15ish then she's stuck by society's rules and has no options to escape other than him.
So far, insufficient evidence to support anything really besides that he's emotionally vulnerable to loneliness.
@Not_tali Ofc it was a lie. Everything about his identity is a lie. However your previous comments seem like you'd be the type to complain about it if he was. Besides Sacchan already said that if they wanted anything more than their current relationship it'd all fall apart which is the author basically saying "I'm gonna milk this as a slice of life repetitive ongoing manga until it gets axed" so you don't ever need to worry about real romance actually happening. Plus this authors other works have tragedy woven into them.