In the vast virtual realm of OZ, a popular digital world in Japan, users create avatars to access a multitude of services from gaming to legal matters. Kenji, a reserved OZ moderator, plans to spend his summer maintaining the system but changes his plans when Natsuki, a classmate, invites him to her family's 90th birthday celebration. To his surprise, Natsuki introduces him as her fiancé, sparking chaos. Amidst his efforts to impress Natsuki and her relatives, Kenji receives a cryptic message, unraveling a chain of events that lead to a catastrophic disaster for OZ.