Mitsu is so precious. And I love that we're getting more Rui. She makes sense to be the insecure one of the four when you think about it. Shou and Kuroki have the confidence of knowing eachother most of their lives, while Mitsu and Rui are relatively recent. Mitsu is also so uninhibited around others while Rui is asocial and doesnt get that stuff. But they have a strong opposites can attract vibe.
Also Mitsu did say she likes the jealous type :3