This Doll Fell in Love. Volume 4.

Marin invites Wakana to a Halloween party and introduces him to her friends there. They start to suspect that they are dating, but Wakana desperately denies it. Meanwhile, the upperclassmen are preparing for the school festival, and Marin has the exceptional opportunity to cosplay a popular host from a shoujo manga! But… is Wakana busy? Will Marin have to sew her own costume? Or will Marin and Wakana's class show themselves to be the most supportive and friendly in any endeavor? New challenges lie ahead, and Marin will surpass herself!