Yuuki Mika

Mika is Saeki's deceased friend, roommate, and primary reserve tank. The two had been friends since high school, and Saeki was devastated at her loss.

She seems to have been a very bright and kind person, having initiated contact with Saeki herself and happily assisting her with things like makeup and housework. She had other friends besides Saeki, but kept them secret from Saeki because she felt the relationship between the two of them could not be explained. She also seemed to wish Saeki were more capable of living without as much assistance. Despite this, she very earnestly cared for her. The two were very close, and their feelings for each other were mutual.