Cooro is a Plus Anima, a boy with the ability to use animal powers. On his quest to find another Plus Anima, he comes across a circus that has a mermaid on display at the sideshow. He gets caught sneaking in without paying, and is captured by none other than the mermaid, who happens to be a fish Plus Anima boy, being made to dress as a princess.

While chasing the girls to get their possessions back, Husky gets his pearls stolen while Senri ends up saving one of the little girls who stole from them. They meet the leader of the thieving girls, who lets them stay because of Senri's kindness, and agrees to help Husky get his pearls back. As it turns out, Husky's pearls were stolen by a bat Plus Anima, a girl named Nana. They pearls are lost in the end, but Nana, after settling a dispute with Husky, is allowed to join the other Plus Anima in their travels.