This new girl Yuu is a landmine girl. And it's not just about her Jirai-kei fashion, if that message window can be trusted.
The big surprise for me is that POV-kun actually has a girlfriend and it's this girl. I should've noticed when the two of them are on a first-name basis, Kazuya and Yuu. I guess that helps explain why he's more confused than delighted that random girls seem to like him. Having a gf who he loves and is trying to be faithful to just means he's not on the lookout for more girls to fool around with.
But in the end I still don't trust that message window, and I kind of like that he doesn't either, since he doesn't have any real evidence yet that what it says is the truth.