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...

Haruto wakes up to the sound of a beeping EKG to find Asahi standing over him. "I'd be surprised if I were you, too. You've been asleep for six years," says Asahi, who came with Satsuki and Takanori to visit him. Asahi explains that Haruto got a game over when he protected Nozomi from Purgatorio. However, Haruto isn't satisfied with the explanation and questions them about Re'Union.

In Re'Union, Haruto retakes possession of Pleiades, which holds the power of the members of Subaru. Clive received a request for help from Elicia, and tells everyone that Elicia says that in order to stop Gnosis from awakening Asahi, it is necessary to awaken all the members of Subaru. Meanwhile, Haruto and Satsuki reunite with Nozomi in the real world, and ask her to log into Re'Union again.

Haruto, Satsuki, and Takanori meet up in real life to discuss how to rescue Nozomi. However, they suddenly find themselves caught up in a strange phenomenon, when a mysterious man appears and tells them that in order to change the future, they need the power to choose an ideal world. Recalling Elicia's story, they conclude that the man must have used one of the Senses from Re'Union in real life.