Kaori lives happily with her husband. One day, while her husband is away on a business trip, the water supply to her home suddenly gets cut off. The reason? A temporary deterioration in water quality at the purification plant. Soon after, a fake water department worker named Shimo-kawa arrives, claiming he needs to inspect the water. Kaori lets him inside, never expecting what happens next—events spiral far beyond anything she could have imagined.