A classmate of Kimito when he comes to Seikain Jogakkou. Aika is a loner who has great trouble socializing with the other girls in the academy. She wants desperately to become popular and convinces Kimito to help her in this pursuit. She and Kimito create the "commoner club," meant to capitalize on the current popularity of anything related to commoners after Kimito's arrival at the academy.
Aika is practically incapable of telling lies, and often says what is on her mind, regardless of how others might react. For this reason she has distanced herself from her classmates. She is also very gullible, causing her to be easily tricked by the mischievous Kimito.