唯井 ふたみ

Saku’s self-proclaimed wife. Appearing on day one in Saku's house, she is a frank, straight girl that is good with housekeeping. While very knowledgeable, she lacks a bit of common sense. Her nickname at school, the Super Saintly Sister, perhaps describes her the best. She represents Gemini.

Her real surname is 雲戌亥 (Kumoinui), which Saku is unable to perceive correctly at first.