Sanae Mizuno is a nurse at Yomiyama Hospital. She is first seen at Kouichi's ward. She has a brother named Mizuno Takeru who went to the class 3-3 at Yomiyama North Middle School.
While on a call with Kouichi in an elevator, the elevator cable snaps and the elevator plummets to the basement of the hospital. She dies upon impact and is buried under falling debris.