Michiru Kaiou was the civilian identity of Sailor Neptune, and appeared in the Sailor Moon anime, manga, musicals, and video games. Michiru was mature, calm, and quiet, and it was hard to tell just what she was thinking. She had a distinct sense of humor, though, and enjoyed teasing Haruka. According to the Materials Collection, she had a kindness "as great as the sea." She was an athletic swimmer, a gifted artist, and an accomplished violinist; she often performed in concerts, either by herself or jointly, such as when she held a concert with the Three Lights. She lived the life of the wealthy Tokyo elite and, in the S season/Infinity arc, attended Mugen Academy, a school for genius students. At the time, however, she attended it to infiltrate its operations.