They are Zashiki-Warashi yokai.Mitsu and Momo bring nothing but chaos. Naturally they enjoy causing mischief and pranks everywhere they go that only their mother Yori or their cousin Erma can put an end to. When encountering their aunts and uncle, they pretend to be innocent.Their father is somewhat of a sore subject. As soon as anyone brings him up by insults, they immediately attack the person who talks about him.