"Lord of Vermilion: The Crimson King" is a 12-episode anime series based on the multiplayer card-based arcade game of the same name. The story is set in Tokyo in 2030, where a mysterious red fog envelops the city, causing widespread panic and chaos. This phenomenon, known as the "Red Fog," triggers a series of supernatural events, including the emergence of monstrous creatures and the awakening of individuals with latent magical abilities. These individuals, referred to as "Awakened Ones," are drawn together by fate and must confront the growing threat posed by the fog and its origins.

The narrative centers on a group of Awakened Ones, each possessing unique powers tied to ancient mythological and historical figures. Among them is Chihiro Kamina, a high school student who discovers his ability to summon a powerful entity known as the "Crimson King." Chihiro is joined by other key characters, including Jun Hiramatsu, a young man with a tragic past, and Tsubaki, a mysterious girl with a deep connection to the Red Fog. As the group uncovers the truth behind the fog, they learn that it is linked to a parallel world and a catastrophic event known as the "Great Collapse," which threatens to merge their reality with a destructive alternate dimension.

The plot delves into themes of survival, identity, and the consequences of wielding immense power. The Awakened Ones must navigate their personal struggles while working together to prevent the impending disaster. Their journey reveals the existence of a secret organization manipulating events from the shadows, as well as the true nature of the Crimson King and its role in the unfolding crisis. The series combines action, mystery, and supernatural elements, culminating in a climactic battle to save Tokyo and the world from annihilation.