While Nerimu's master tries to recruit Yoneko to be a slumber agent, Nerimu thinks that is a terrible idea and tries to do everything he can to keep her from following in his footsteps.
Yaneko loves to sleep, but when she is awakened by Nerimu, an ancient sleep spirit, she agrees to become his assistant, traveling to give the gift of sleep to people and animals, although she is not sure why he has chosen her.