Kagami Sumika

Takeru's childhood friend and classmate. They've been together for so long that he can't imagine what life would be like without her. She has a long-standing crush on Takeru which he is oblivious to.

She takes in Kasumi when she transfers to their school, and they are together at all times.

She wakes him up at mornings, and since her room's window is only a few meters away from Takeru's, they (including Kasumi) can talk before going to sleep too.

Her being a bit of an airhead leads Takeru to tease her often, to which she retaliates by hitting him due to her very short temper.