Saionji Sekai♀

Sekai Saionji is a student in year one of class three who is the antithesis and foil of Kotonoha. A playful and outgoing classmate seated directly next to Makoto, she takes a curious interest in him during their first acquaintance, and in every medium of the series, helps to establish his bond with Kotonoha. Though genuinely upbeat, Sekai does occasionally show a more serious side, and when sufficiently frustrated can be loud, selfish, overemotional and even manipulative. She lives with her mother Youko in the fictional area of Motehara-Sakashita and works part-time as a waitress at the family restaurant Radish.

[From Wikipedia]