Котеґава Чіса

Chisa Kotegawa is Iori's cousin and a first-year mechanical engineering student at Izu University. Chisa appears to more level-headed and serious compared to other characters. She has a clear dislike for rowdy behavior and can be quite hostile, especially when it is directed towards her (especially with Iori). She rarely takes part in drinking or crazy antics and is usually seen sitting off the side as an observer. She loves diving and looking at diving equipment. Chisa is one of three female students in her class idolized by her male classmates due to her major's lack of females.

It is later revealed that she and Iori are not related by blood since Iori's father is adopted by her maternal grandparent.