Marina Takasugi is the younger sister of the local boxing champion. Her introduction occurs when Eiji Akagi encounters her. Eiji, the second son of legendary boxer Keijiro Akagi, is a high school dropout with no talent for rock guitar and a strong aversion to boxing. Meeting Marina ignites Eiji's sudden and unexpected interest in the sport he previously disliked. This shift in Eiji's attitude defines their interaction, positioning Marina as the catalyst who propels Eiji's engagement with boxing. Her character serves this specific function in relation to Eiji's motivation and development within the narrative.