I was surprised to see Rich Boy and Jailbait in the same scene. Unless they were visiting Sister, it's hard for me to see why they'd bother to meet at all.

It was also weird to see MC drop his poncho before he left, but I suppose he might be giving her some fire protection for the trip down.

Based on just anime content thus far, I didn't see much value in the demon girl's presence besides giving him someone to talk to, and establishing that NPCs can indeed break their command. She was tasked with protecting a place, but decided that for her survival she can choose to do otherwise.