Kokone Morikawa, a high school student in near-future Japan, lives with her mechanic father Momotarō while grappling with vivid dreams of Heartland—a fantastical realm where she becomes Princess Ancien, wielding a magic tablet to animate mechanical constructs. These visions intertwine with political strife involving Heartland’s king and advisor Bewan, mirroring the unresolved tensions in Kokone’s reality: her deceased mother Ikumi’s pioneering self-driving car technology, suppressed by her grandfather Isshin Shijima, chairman of Shijima Motors.

Initially resentful of Momotarō’s secrecy about Ikumi’s past, Kokone discovers Heartland’s allegorical ties to her family’s history, particularly Momotarō’s crafted narratives preserving Ikumi’s legacy. When Momotarō faces false corporate espionage charges, Kokone secures her mother’s research tablet, targeted by Shijima executive Watanabe. Her journey unveils Heartland’s symbols—Ancien embodying Ikumi’s idealism, Peach reflecting Momotarō’s youth—while lucid dreams reveal Ikumi’s fatal accident during a self-driving car trial, bridging her understanding of loss and innovation.

Kokone’s defiance against Watanabe parallels Ancien’s clash with the molten Colossus, culminating in a duel that resolves both realms’ conflicts. Her efforts reconcile Isshin, who reinstates Ikumi’s project for the Tokyo Olympics, symbolizing technological and familial healing. Kokone evolves from a stress-prone dreamer napping to escape reality into an active guardian of her heritage, aided briefly by childhood friend Morio. The self-driving motorcycle Heart emerges as a testament to Ikumi’s enduring impact.

Expanded through a spin-off film exploring Heartland’s lore and a manga reaffirming her journey, Kokone’s story remains consistent—her optimism anchoring the interplay between mechanical legacy and fantastical introspection.