After numerous experiments with creating autonomous AI, humans concluded that AI could only be functional if they were given just a single mission to dedicate their lives to. With that in mind, the first autonomous AI, a songstress named Diva, was created with a mission to "make people happy with [her] songs". However, Diva's quest to sing on the main stage of the theme park NiaLand is disrupted by the arrival of Matsumoto, an AI from 100 years in the future who tells her of a world where AI have decided to eradicate humanity, and wishes to join hands with her to prevent it.