These monsters have a very cool design, but it has a sort of NSFW story to it which will be discussed later. Let’s start with what it is for now. Basically it’s a turban snail demon. When these shellfish reach the age of thirty, it gains a monstrous form, as well as various shape-shifting abilities.

It’s specific behavior is a bit of a mystery, at least to me. Some writings only indicate its desire to ride the waves under the light of the moon. Another describes it as predatory with a penchant for mischief. It prowls the coasts at night looking for prey, it’s known to break in to seaside homes and eat the residents. But perhaps a folktale involving er… let’s just say frustrated pirates made the Sazae Oni gain notoriety.