Mari Tamagawa is a fictional pop singer created exclusively for the anime adaptation, never physically appearing within the story. Her presence manifests solely through audio broadcasts and a single visual concert poster. Her music serves as a key motivational force for character Keiichirou Asano, who regularly listens to her songs on his MP3 player en route to games. Capitalizing on this fandom, another character orchestrates a crowd performance of Asano's favorite Tamagawa song during a pivotal match to energize him. Songs attributed to her character, including "If" and "Ready Go!", are commercially released singles performed by Megumi Nakajima. The character originates entirely from the anime and lacks any established background or personal history. She remains absent from the original novel and manga source material.