Sodachi Oikura

Araragi's childhood friend. She is a student with a strong sense of competitiveness which led to her popular nickname, much to her chagrin. Sodachi was the president of a first-year class where both Hitagi and Koyomi also belonged to. At school, she wanted to be called as "Euler," but ends up getting the nickname "How Much," a pun on her surname (お幾ら, o-ikura) and a reference to her personality. (Source: Bakemonogatari Wiki)