A young wavemaster, known only by the alias Tsukasa, awakens in an MMORPG titled The World, suffering from slight amnesia. He has no recollection of his actions prior to waking up. Within The World, the Crimson Knights suspect him of being a hacker, having witnessed him accompanying a modified character in the form of a cat. Unable to log out of the game, he wanders in search of answers, evading the knights and other players he encounters along the way. As Tsukasa explores The World, he comes across a magical item that takes the form of a "guardian," which promises him protection from all harm. Subaru, the leader of the Crimson Knights, along with several other players who have become acquainted with Tsukasa, set out to investigate why Tsukasa cannot log out, attempting to resolve the issue before it escalates.