故事发生在冈山县仓敷市，高中女孩森川心音（高畑充希 配音）与父亲桃太郎（江口洋介 配音）相依为命。心音最为擅长的就是睡觉，无论身处何方，只要她想似乎就随时可以进入梦乡。不过最近一段时间睡觉让心音有点儿闹心，因为反反复复她总是做同一个梦。而父亲似乎只对改造汽车感兴趣，对女儿的烦恼全然没有半点察觉。2020年，就在东京奥运会召开前三天，桃太郎突然被警察逮捕。心音坚信父亲绝对清白，于是她找到童年时的好友，正上大学的佐渡守生（满岛真之介 配音），结伴前往东京拯救父亲。在此途中，女孩不断从自己的梦中得到启示，而这些恰恰成为解开父亲被捕之谜的谜团。因此，心音决定利用自己的睡觉技能，完成这次交织着梦和现实的冒险之旅……

Smartphones, computers, gaming consoles or digital tablets are now givens in our daily lives. The electronic intrusion is causing controversy and collective hysteria. Are we damaging our brains with all these screens? How will unprecedented exposure to screens impact humanity? To find out, the filmmakers examine how science has been applied to distinguish between truth and falsehoods, and explore the suspected side-effects of screen exposure. The documentary travels through the US and Europe to meet and speak to researchers who are leaders in this field.