The next few chapters gonna be difficult to read because of things I imagine will happen, like:
1. Those two new characters will definitely look down on Yuu again, throwing his self-esteem even further into the ground;
2. The sisters will try to defend him, but Yuu himself will stop them, mainly because his thinking that could harm the sister's image for the commercial;
3. The climax could be the new characters humiliating Yuu, somehow throwing his mother's name into the mix, making him cry or get super depressed, making the sisters finally snap at them;
It's just a theory, but that's what I'm expecting before everything starts to get wholesome again, and by that I mean the sisters helping Yuu getting over his low self-esteem and showing those two how amazing he really is.