"Attacker You!" is the story of ambitious and energetic thirteen-year-old junior high schoolgirl You (pronounced Yu) Hazuki, who moves to Tokyo from the Japanese countryside, where she lived with her grandparents, to live with her father Toshihiko, a cameraman recently returned from Peru, and attend Hikawa High School. You's mother is not in the picture, having left when You was very young. Also living with You and her father is her adoptive younger brother Sunny (adopted by Toshihiko while he was in Peru), who is very attached to his stepsister and tends to follow her everywhere she goes, including to school and to her volleyball matches. However, You's father is not supportive of her volleyball playing, and You is puzzled as to why he gets so angry about it. You is also a fan of Kanako Tajima, a television color commentator for volleyball games, and notices that her father also acts strangely whenever she watches Tajima on TV or sees a picture of her.