Yuu

Yuu is a quite, calm and easygoing guy who is something of a ladies' man, but he can also be very protective of women when he sees them in trouble. He enjoys teasing his sister about her relationship with Rito, like mentioning him in front of her and their parents. Sairenji Akiho is someone Yuu is currently dating, but she isn't taking it as seriously as he does and he feels disappointed every time she turns down his invitations with some excuse. Yuu first noticed Rito when he saw him trying to defend Yui, and has since been interested in keeping track of his sister's relationship with Rito. After finding Rito and Yui being chased by hoodlums, he beats them up easy without being seen from her sister and the boy. Noticing Yui's interaction with a boy like Rito, he hopes Yui will grow to be more mature. He would often mention his name at home in front of Yui, just to make fun of her. He meets Rito directly when he come to their house to give Yui her homework because she caught a cold and didn't come to school. Yuu insists Rito to meet with Yui and, he later mistakes an embarassaring situation between Rito and Yui before leaving, thinking her sister made much progress and this was unexpected. After speaking with each other (and sharing a beating from Yami, due to him complementing her clothes and Rito getting into a perverted mishap), he understands more about Rito's life with aliens and all the misfortunes happening around him. He sympathizes with Rito, but remarks that at least his life is more exciting. Rito seems to like Yuu, as he finds him to be a really cool and understandable person. He is one of several people who knows that Yūsaki Riko is in fact Rito.