Rei Koito

Rei is Yuu's older sister and a university student. Yuu calls her "Rei-chan." Unlike the serious Yuu, Rei has a laid-back personality. She is dating Hiro-kun (Hiro Otsuka, voiced by Kengo Kawanishi), her boyfriend since high school, and their relationship is recognized by the family, as they often have dinner together at the Koito household. Rei is the only one in the family who has noticed the relationship between Yuu and Touko, and despite knowing it's a special relationship, she supports Yuu, who has developed "special" feelings. Rei's hobby is baking, and she sends Touko the recipe for Yuu's favorite cheesecake along with a picture of Yuu sleeping. In the final episode, Rei is married and has returned to her family home because Hiro-kun is on a business trip. She encourages Yuu, who is about to go out, to live together with Touko.