Mitsuhiro Sachi

Sachi is a girl with an energetic and vibrant personality, at odds with her habits of dozing off at school and procrastinating whenever an opportunity to do work presents itself. She is hardly fazed by Kenichi's exterior and is the first to become friends with him. An orphan, she earns money through internet speculation, and shares her apartment in the school dormitory with a little girl from the Southern Country named Mana. In the past, she had a hobby of painting, but she has not done this since her parents died.

Her obligation is to have a "12 Hour Day" - after being awake for twelve hours, she must 'stop' by taking medicine which knocks her unconscious for another twelve hours. This medicine is not particularly effective at relieving fatigue, and she often naps for a good portion of the remaining hours.