Tsukibashi Sayo

The main character of the story. She has the mind of a genius and her brains have been put to use at the research establishment since she was young.

It was decided that Mirai's upbringing would be left up to her.

She is a girl, but her manner of speech is boyish and cold. She is rude towards those who are close to her. Basically, she's not very good at much else except using her head.