Riko Sunomie is one of the main characters in the anime and manga series 'Kiss x Sis.' She is one of the two older stepsisters of the protagonist, Keita Suminoe. Riko is characterized by her playful and teasing personality, often showing a mischievous side when interacting with Keita. She has strong feelings for him and is not shy about expressing them, leading to numerous comedic and awkward situations. Riko is known for her energetic demeanor and is often contrasted with her more reserved sister, Ako.