Ai Fuyuumi
A-chan, Love Princess, 冬海 愛衣
This individual is a strict member of the Student Councils Hallway Monitoring Committee who frequently scolds Chiwa for misbehaving in the corridors. It appears that she has known her friend Kaoru since they attended elementary school together.
Spoilers:
She is actually his childhood friend, whom he met 1 year before Chiwa. Ai and Eita went to the same kindergarten. She is also actually Eitas fianceé; they got engaged in kindergarten.
