Kokone Morikawa suffers from a weird napping condition that distracts her from reality, rendering the worlds of her dreams and reality nearly indistinguishable. In reality, she is a typical high school student studying for her university admission tests; yet, in her dreams, she is a mythical princess of Heartland, a machine-driven future in which the use of artificial intelligence is prohibited. Within the seemingly fictitious dreamland, Kokone learns more about her family's history and the mystery that her father, a gifted mechanic, has sought to keep hidden from her. However, when the events of two universes become intertwined, she must now safeguard the secret from malevolent beings both dream-like and terrifyingly real.