Chōun is a mysterious girl who appears calm, collected, and very powerful. She is the second person to join the group. She loves to tease Kan'u and other women frequently, and seems to relish whenever she gets up close with them. She also assumes the identity of a hero of justice named Butterfly Mask (Kachō Kamen), hence wearing a butterfly mask.
Chōun is scary when she's smiling (Sui will have nightmares about it and Shion won't let her daughter sees Chōun's smiling face). Chōun even continues teasing Kan'u in more ridiculous ways (like an embarrassing introduction of Kan'u to the bandits who attacked Ryūbi - and Chōun gets a lump on the head as a result).
