Haseo, Takahiro Sakurai, is a skilled player in the popular online game The World who sets out to track down a notorious Player Killer named Tri-Edge in order to save his real-life friend Shino, who lies comatose after a PK incident. His search leads him to a girl named Atoli, Ayako Kawasumi, who shares Shino’s PC after a dispute with her superior Sakaki over PKK activities, and he crosses paths with Ovan, a former guild master who hints that Tri-Edge will surface again at the very place Shino was PKed. Haseo’s pursuit culminates in a fierce fight against Tri-Edge, but he is defeated and loses all his PC’s powers, leaving him vulnerable and adrift.
Defeated and disoriented, Haseo is captured by a group of CC Corp system administrators called G.U., led by Yata, with Pi and Kuhn as his subordinates. G.U. explains that Haseo is one of the special Epitaph Users who can control a powerful being known as an Avatar, and they offer their help in locating Tri-Edge in exchange for his aid in eradicating a dangerous AI bug called AIDA that has left multiple players in comas in the real world. Wary yet hopeful, Atoli approaches Haseo and spends time with him, but he rejects her in a moment of anger. Ovan, the former guild master, manipulates Atoli into searching for Tri-Edge to win Haseo’s approval.
As Atoli’s disappearance—tied to the AIDA phenomenon—drives him onward, Haseo teams up with Pi and Kuhn to track her down. When Tri-Edge reappears, Haseo awakens his Avatar, Skeith, and defeats his nemesis. Yet the victory is shadowed by tragedy: Atoli is attacked by AIDA, and her PC data begins to deteriorate. To save her, Haseo shares his PC data with Atoli, a risky move that sets off a chain of events across digital and real spaces. Ovan hacks into G.U., transporting Haseo and Atoli into Atoli’s mind space, where Haseo confronts the AIDA-infected Atoli and frees her from its influence.
Returning to the real world, they discover Pi and Kuhn’s PCs destroyed, leaving behind a Tri-Edge sigil as a grim sign. Ovan reappears with an unsettling reveal: he bears an AIDA arm and confesses to being the true Tri-Edge who killed Shino. The revelation shakes Haseo to his core, but Atoli helps him remember the true reason he fights, empowering his PC once more. Haseo’s rage surges, yet ultimate victory comes through a renewed sense of purpose rather than sheer anger. It is revealed that Ovan’s actions unintentionally left his sister Aina comatose after being infected by AIDA, and to save her—and purge AIDA—Ovan sacrifices himself by waking Aina, a heartbreaking but necessary choice.
With Ovan’s sacrifice clearing a path, Atoli uses her Avatar’s power to send Haseo into the sea of data to reach Ovan and rescue him in spirit. After the climactic battles, Haseo reunites with Atoli at Hulle Granz Cathedral, where Shino awakens and blesses their budding relationship, signaling a hard-won peace and a future built on trust. In the post-credits scene, Aina is shown playing on a field with Ovan nearby, while Pi’s player Reiko Saeki receives a call from an unknown man reporting that the threat has been dealt with and a group known as Schicksal is on the move.
