Supporting character in Seitokai Yakuindomo. A hardworking judo fighter, Mutsumi's innocence and purity are such that she's almost always asking either Hagimura Suzu or Tsuda Takatoshi about what the othertwo members of the student council are talking about, to which they never answer. She has long black hair often kept in a ponytail. Seems to have feelings for Tsuda.