The story begins with Yoshiki Nishida, a self-proclaimed game enthusiast, meeting with his two friends, Hisashi and Kazuki, at a bar. They reminisce about their shared passion for the online game "Grandia Seed," which is scheduled to shut down the next day. Despite its reputation as a "kusoge" (crappy game), Yoshiki found its combat system unparalleled, dedicating significant time to it, earning him the nickname "Combat Maniac." His friends, having mostly transitioned to using the game as a chat tool, are less invested in its final hours. They discuss their plans for finding a new game, with Kazuki, a subculture aficionado, being more proactive than the more casual Hisashi.
After returning home, Yoshiki logs into "Grandia Seed" and joins his team chat. He notes the low player count, even on the eve of the game's closure. His friends, Hisashi (using the in-game name Daria) and Kazuki (Syun), eventually join. Yoshiki is surprised by Daria's character choice: a blonde, bob-cut elf loli. Syun, in contrast, created a character resembling himself, a short human male with white hair. The team discusses the upcoming server shutdown and the possibility of increased logins. Yoshiki, meanwhile, focuses on his unique weapon, the "Daken" (Soul-Stealing Sword), a low-attack power but high-rarity weapon that allows him to absorb enemy abilities. He manages to acquire a new, powerful ability, "Throne of the Usurper (Dragon)," which halves dragon damage and multiplies experience gained from them.
As the game's final hours tick down, Yoshiki and his team engage in a frantic effort to acquire more abilities from powerful boss monsters. The game developers seem to have increased drop rates, allowing Yoshiki to amass a significant number of new abilities. The team gathers in the central town for the countdown event, witnessing an unprecedented player turnout, a testament to their shared love for the game despite its flaws. Yoshiki, in his elaborate "Demon Lord" avatar, attracts attention. He then decides to challenge the game's final boss, "Creation God Astral," to acquire one last ability.
After a grueling battle, Yoshiki defeats Astral, completing his "Throne of the Usurper" collection. However, upon attempting to equip all the "Throne" abilities, nothing special happens, a typical "kusoge" anticlimax. As the server countdown reaches zero, Yoshiki's consciousness fades.
He awakens in a cold, unfamiliar forest, finding himself not in his room but in the body of his "Grandia Seed" avatar, KaiVon. He is wearing KaiVon's distinctive black coat and has the demon lord-like appearance he had customized. He encounters a giant snake and is saved by a woman who identifies him as a powerful demon. This woman, who reveals herself to be Rue Semiele, an elf, explains that this world is protected by a powerful barrier, and she cannot leave its vicinity. Rue, who can also access a status screen, is surprised by Yoshiki's human origins and his ability to use the menu.
Rue takes Yoshiki to her home, a log cabin, and they begin to bond. Yoshiki learns that Rue has been in this world for an incredibly long time, possibly since the "Genesis Era," and has been tasked with sealing a "Dragon God" using her immense magical power. She explains that the "Gods' Era" was when unseen deities ruled, and the "Genesis Era" was a period of upheaval following their departure, marked by the emergence of new "Seven Stars" and the development of magic and nations. Rue's inability to leave the area is due to her role in sealing the Dragon God.
Yoshiki, having mastered his "Daken" and his in-game abilities, is now capable of fighting powerful monsters. He trains with Rue, learning to use magic, and discovers he has an affinity for fire and ice, and eventually, darkness. He also learns that his "Grandia Seed" avatar's appearance is his default form in this world.
After a year of living with Rue, Yoshiki decides it's time to leave the forest and explore the world. Rue, though initially hesitant, eventually agrees to accompany him, revealing that the Dragon God he defeated was the source of her confinement. They discover that the world has changed significantly, with the landscape altered and the "Guild" system now a prominent part of society. They also learn about the "Gods' Era" and the "Genesis Era," and that Rue's friends from "Grandia Seed," Daria and Syun, are also present in this world, though Rue has not met them directly. Yoshiki realizes that his actions in "Grandia Seed" have been mythologized in this world, and that Rue is a being he created and nurtured within the game. Together, they set out to explore the world, with Yoshiki now possessing immense power and Rue having been freed from her duty.
