Nichijou Nendoroid Actionfigur Hakase: Keiichi Arawi Ver. 10 cm

Hakase is an 8-year-old scientist who, despite her outstanding intelligence, often still acts like a child.
She loves sharks and snacks, and constantly modifies Nano, whom she created, adding strange and unusual functions such as a roll cake dispensing arm. Nano is usually unaware of these modifications until they are first used. Hakase always refuses to remove the obvious wind-up key from Nano's back on the grounds that it is cute, despite Nano's regular requests.
Hakase does not go to school (apparently because she has already graduated) and spends her days playing around in the house instead. Hakase's family is never revealed, though she may be related to the Principal of Tokisadame Highschool since they share a surname. She lives with Nano and Sakamoto.

(Source: Nichijou Wikia, edited)