Aika Sakuranomiya

She is Maika Sakuranomiya's older sister and Kōichi's younger sister. She is a traditional Japanese beauty with long black hair and wearing a kimono. She worries about Maika, who has few friends due to her unfriendly looking eyes, but tends to overcare along with Kōichi, often making Maika feel annoyed. Unlike Maika, Aika does not have unfriendly looking eyes but has a natural sadistic streak. She mistakenly thinks Dino is Maika's boyfriend and often gives advice. Since being bitten by a neighbor's dog along with Kōichi after splashing the dog with water guns as a child, she is afraid of dogs. Maika calls her "Aika Onee-san" or simply "Onee-san."