Karin is a popular girl at Haru's school. After Ten mistakenly confesses to her instead of her older sister, she agrees to give him relationship advice in exchange for Ten providing the same regarding his older brother, whom Karin has a crush on.
Later Karin reveals to Ten that she likes him and not his brother, clarifying that she wished to get closer to Ten without having him distance himself from her due to his existing crush on her sister. Afterwards, Karin issues a new challenge to Ten for the future: to see which of them can enter a relationship with their loved one first.
