Matsuri Amachi was Makoto Yūki's childhood friend within their group. Before Mochizuki Academy closed, forcing their separation, she achieved high grades and actively studied with friends to ensure they all attended the same school, driven by a desire to keep their friendships intact. During this time, her personality was cheerful, moody, and somewhat daring; she participated in pranks with Makoto despite their antagonistic dynamic, often entering his room through the window. She was emotionally sensitive, tending to take personal comments seriously and holding onto perceived slights. After the school's closure and three years apart, Matsuri attended the local elite girls' school Gekka while others moved away. This separation significantly altered her. Upon reuniting at the abandoned school, she had become taciturn, anti-social, inarticulate, and outwardly cold, largely due to internalizing Makoto's past comments too seriously. Her appearance changed: her height was noted as 150 cm or 155 cm, her hair was shorter and styled with either a hair ribbon or tied back with a yellow headband, though she retained her green hair and green eyes. During the reunion event focused on finding their buried time capsule – hidden by their teacher – Matsuri initially showed reluctance to engage and irritation toward Makoto. Despite her distant demeanor, underlying emotions from their past friendship persisted. An incident involving a rat in a lavatory caused her to scream and flee in panic, revealing vulnerability beneath her reserve. Interactions during the search for the capsule and shared memories gradually prompted a cautious reopening to her friends. Her relationship with Makoto remained complex, characterized by a history of love/hate interactions and unresolved tensions from their separation. She questioned him about his lack of contact with Nono Nekomiya, indicating her continued awareness of group dynamics. The core of her character arc involves reconciling her lingering affection for her childhood friends with the defensive coldness she developed, driven by emotional sensitivity and a fear of rejection.