In the online RPG "Union" was Subaru, a party of grade school players. One day, two of its members Asahi and Haruto exchanged a promise and a ring. But Asahi sacrificed herself to protect Haruto and also died in real life. The game then suspended operations and the members of Subaru went their separate ways. Six years later, Haruto logs into the newly released "Re'Union" and reunites with Asahi.

Haruto is shocked by Asahi's sudden appearance in Re'Union six years after her death. Asahi acts as if nothing has happened, although she's unable to log out from the game. Players have noticed Asahi's existence and try to take her, but the former Subaru member Takanori appears. He had become the leader of the elite guild Illuminati. Asahi suggests reassembling Subaru, but...