Mutsumi is 22 years old, and much to her own surprise speaks with a Kansai accent for no apparent reason (translated in the English dub as a Brooklyn dialect). She has something of a complex about the small size of her breasts, and possesses probably the most useless power of all the seven sisters - the Earth Breakfall, which means she can fall over safely. Her name is derived from mutsu, the Japanese word for "six" (for which another word is "roku"), being the 6th of the Sisters.

from wikipedia