In 2045, artificial intelligence has replaced most human labor. Jun is the only human employee at an automated VR-device factory, retained because the law requires at least one percent of the workforce to be human. Trapped in a repetitive life, he spends each evening playing the virtual-reality game Oz.

A new story-mode season offers its winner a single wish. Jun enters with basic equipment, hoping to become the Lord of Emerald City. Inside the game, he meets Tin, an outdated AI companion who has continued waiting for his absent owner, Rosie. Tin possesses a Golden Butterfly that permits entry to the story mode but appears to survive only because of hacking and system errors.

Jun invites Tin to join him and promises to help him obtain a human heart. Although Tin does not understand what that means, they begin completing quests and collecting items together. Tin’s abilities are limited, but his sincere concern and unexpected choices help Jun recognize value in things—and people—that society has discarded.

Their principal rivals are Max, an elite player who has spent heavily upgrading his older AI companion, Button. Max dismisses Tin as defective and warns Jun that bringing him before the Wizard could expose the system error keeping him alive and lead to his deletion.

After completing the final quest, Jun reaches the Wizard and receives the promised wish. He abandons his dream of ruling Emerald City and instead asks that Tin be allowed to exist legally within Oz.

Back in the real world, Jun once again orders an iced Americano but receives a hot one. He and the café worker finally recognize each other as Jun and Max, unaware until then that they had crossed paths every morning. Leaving their rivalry inside the game, they agree to meet again.