Makoto is happily married to Mariko, his older former coworker, until his jealous boss warns that quiet beauties like her are the most likely to cheat. Growing anxious, Makoto gives Mariko, who still uses an old flip phone, a new smartphone with a location-tracking app installed. One day, while monitoring her movements, he watches the marker head into a love-hotel district. It then remains motionless inside a hotel for three hours.