She is Tensai's assistant, where they maintain a sort of Sherlock Holmes and John Watson-like relationship. Though she may look like a girl, she is actually a gender non conforming Male, and is honest about this if it is relevant. Daruku, along with Tensai, transfer into Juugo's school where they are also the his classmates after their brief visitation at the his apartment where they also met Nanana. Daruku also becomes a member of the "Adventure Club" since she goes wherever Tensai goes.

(Source: AniLinkz)