In the year 21XX, declining national morale has prompted the Japanese government to establish the Ministry of State Happiness. Its solution: a virtual recreation of early 21st-century Japan called the Habitat, maintained inside a cold-sleep network called Clover. One hundred citizens, connected while asleep, live in the Habitat as avatars and generate what the government calls happy energy, which Clover collects and redistributes. One day, all one hundred avatars stop functioning simultaneously — and an unauthorized 101st person is discovered to have connected to a system built for exactly one hundred. The Ministry urgently summons a scientist with authority over Clover: a Happiness Manipulator, tasked with going in and finding out what went wrong.