In a world where assassins wield deadly skills, the notorious Assassin of Crimson stands out as the most lethal. Once the revered leader of the Yuuyami Assassin guild, this enigmatic figure is infamous for slaying King Mars, the ruler of the land. In response, the princess offers a tempting reward: her hand in marriage and the throne to the one who apprehends the Assassin of Crimson. Enter Virgil, a red-haired individual often mistaken for a girl, traveling with a troupe as he seeks his missing twin, Serge. Strangely, Virgil's appearance aligns with the descriptions of the elusive assassin. As Virgil's journey unfolds, he delves into the truth behind the king's demise and the true identity of the Assassin of Crimson.