Isshin Shijima chairs Shijima Motors in reality and rules as monarch over the vehicle-manufacturing dream realm of Heartland. His real-world dismissal of daughter Ikumi's self-driving car project created a deep rift, leading to her estrangement. This mirrors his Heartland counterpart's rejection of Princess Ancien's magic tablet usage, resulting in her confinement.

After Ikumi dies in an accident during a software test, Isshin revives her abandoned self-driving technology for presentation at the 2020 Tokyo Olympics as a legacy tribute. This action triggers corporate espionage conflicts within his company. In Heartland, his regret shifts his perspective: the King recognizes advisor Bewan (Watanabe's counterpart) as a threat, arrests him, and actively defends the kingdom.

His arc concludes with reconciliation. He acknowledges Momotarō's role in preserving and advancing Ikumi's work and seeks a relationship with his granddaughter Kokone, signaling healing for familial wounds and acceptance of both technological progress and the family he once rejected.