Oneechan ga Kita

Tomoya Mizuhara, a 13-year-old boy, finds himself with a new older sister after his father remarries. His sister, Ichika, is 17 and has a somewhat eccentric personality, often expressing overly intense affection for Tomoya. Ichika's friend Ruri is known for her sadistic tendencies, while Ichika's friend Marina, who is quarter-Japanese, stands out for her physical appearance.