Shichisei no Subaru unfolds around Union, a world-renowned online RPG where a legendary party called Subaru once stood out. Formed by childhood friends Haruto Amou, Asahi Kuga, Satsuki Usui, and the rest of their close-knit group, Subaru shared victories and losses inside the game until a tragedy shattered both worlds: Asahi died while playing, and Union shut down soon afterward. With Asahi gone, the members of Subaru go their separate ways, and the bonds that defined their childhood slowly fall apart.
Six years later, Haruto, now a high school student, logs into the renewed Re'Union and is stunned to find Asahi again. Whether she is truly Asahi or only an electronic ghost left behind by the system becomes the mystery that draws the former members of Subaru back together. As they re-enter the mysterious and deadly online game to uncover the truth, returning to that world becomes both a second chance and a burden. Old bonds are tested, the pain of their separation resurfaces, and every answer seems to open the door to a new danger as Subaru confronts the possibility that recovering the past may demand more than simply logging back in.