Kotegawa Yū

Yuu Kotegawa is Yui's older brother, and a ladies' man, which she dislikes about him.

Biography
After finding Rito and Yui being chased by hoodlums, he defends the two of them from the ruffians, while commenting that he hopes Yui will grow to be more mature.[13] Since then, he has taken notice of Yui's relationship with Rito. He can easily read his sister's poorly hidden feelings and her love for Rito, and is eager to see his sister become more open to romance through Rito. He is one of the few people who knows that Riko Yuusaki is in fact Rito.

At the moment, he is dating Akiho, Haruna Sairenji's older sister, but unknown to him she isn't taking the relationship as seriously as he does.[14]