Momotarō, a skilled car mechanic and single parent in Okayama Prefecture, navigates life after losing his wife, Ikumi, in a crash during her self-driving software’s test run. His guarded nature and avoidance of Ikumi’s memory strain his relationship with his resentful daughter.

A cracked tablet holding Ikumi’s proprietary technology—once dismissed by Shijima Motors but later sought for Olympic demonstrations—fuels accusations of corporate theft, triggering his arrest and propelling his daughter to unravel their family’s secrets.

In allegorical bedtime tales, he becomes Peach, a motorcycle-riding ally to Princess Ancien in Heartland. These layered stories, mirroring Ikumi’s innovations and struggles, weave her legacy into fantastical narratives, allowing him to honor her memory obliquely.

His quiet expertise extends to clandestinely upgrading vehicles with autonomous features, unpaid yet driven by loyalty to Ikumi’s vision. This silent dedication highlights his principled resilience amid financial hardship.

The story’s climax intertwines reality and fantasy as he emulates Peach’s heroism, risking his life to save his daughter. This act mends their fractured bond and spurs reconciliation with Isshin Shijima, Ikumi’s estranged father, uniting them to fulfill her unrealized project and cement her technological legacy.