On June 6, 2031, elementary school student Yuuma Ashihara participates in the playtesting of a revolutionary virtual reality MMORPG called Actual Magic. He is initially amazed by the game's realistic fantasy world, but the experience quickly turns into a nightmare when he attempts to log out. The boundaries between the digital realm and the real world begin to fuse, causing chaos to engulf his reality.

As the fusion takes hold, Yuuma discovers that the game mechanics and monsters are manifesting in his own town. In a desperate search for answers, he encounters his classmate Sumika Watamaki, who was previously considered one of the cutest girls in their grade. She has undergone a horrifying metamorphosis, transforming into one of the game’s terrifying monsters. Yuuma realizes that this is no longer just a game; staying alive is the beginning of a new, deadly challenge where death lurks around every corner.

The story follows Yuuma and his twin sister, Sawa, as they navigate this new hybrid existence where the rules of Actual Magic apply to the physical world. As they fight for survival, they meet other classmates who have also been pulled into the crisis, each potentially gaining unique abilities tied to in-game classes such as Magician, Warrior, Monk, Thief, or Hunter. Yuuma himself takes on the role of a Tamer or Monster Tamer, allowing him to command creatures in this mixed reality. The central conflict revolves around understanding why the game is consuming reality and finding a way to reverse the process while dealing with the threat posed by transformed individuals like Sumika.

The narrative is structured around several key arcs. The story begins with the Reality Erosion arc, covering the initial disaster and the immediate struggle to understand the rules of the fused world. This is followed by the Otherworld Manifestation arc, where the game world expands further into reality, and the survivors begin to establish a semblance of order and discover the extent of their new powers. Later arcs, such as Demon Awakening and Hegemony Battle, focus on the rise of powerful foes among the survivors and the ensuing power struggles as different groups vie for control over the fate of the new world. The manga presents a unique take on the death game genre, moving beyond pure virtual reality into a state where game and reality are one and the same.