A Mecchii is being beaten up by a Amanojaku in Ice Book due to being a pacifist. Scared at the sight of a Devil Child, but relieved when he warns her not to watch out. Once Akira defeats Amanojaku, she thanks him by revealing that there's a secret chest in the caverns of Akuma no Hokora.
In the anime Mecchii is the seventh demon that become an ally to Setsuna and Mirai. She is first thought to be male and become Cool 's "Little Brother". In her debut episode she defeat Mizuchi, Abaddon, and Fenrir with her lightning abilites. She is confirmed female because she is unaffected by Nekomata 's charm. Mecchii is one of the only two demons to return in the second part along with Jack Frost.