Mutsumi Aasu, the second-oldest of seven sisters in the Aasu family, juggles college demands amidst her household’s chaotic environment, ill-suited for focused study. Her name, rooted in the Japanese word *muttsu* (six), aligns with the sisters’ reverse numerical naming tradition. Plagued by self-doubt over her moderately developed figure, she harbors A-Cup Angst, frequently clashing with her sister Shii, who mocks her chest’s stagnation since middle school. This insecurity fuels her longing for magical bust enhancement.

As part of the Earth-defending team, Mutsumi wields Earth Breakfall—a defensive ability allowing safe landings from falls—though its limited combat utility mirrors the sisters’ age-diminished powers, reducing their collective role to symbolic gestures. Initially opposing Poemi Watanabe’s stay, she grows suspicious of Poemi’s motives post-transformation into a magical girl. Mutsumi’s stress-prone nature intensifies under household disruptions and the sisters’ waning magical relevance.

Her speech blends a Kansai dialect, adapted to a Brooklyn accent in English dubs—a quirk she occasionally ponders in-universe. Designed as an expy of *Excel Saga*’s Ropponmatsu, her role reinforces the series’ self-referential narrative framework.