Kuukyo Ai grew up deprived of affection. As a result, he can't identify what others are feeling unless it's visible or implied. His denseness and robotic identification of emotions caused him trouble which he can't live with. When he met Hajime Natsuhi, a transferee in his school, he begins to explore these feelings he was missing as a child. His life changed when he meets Hajime under the school's tree on the last day of spring, the beginning of Summer.