A protagonist named Daisuke, exhausted from the abusive conditions of a black company, finds escape through his devotion to a streamer he adores: the petite demon lord Karna. In a surprising turn, Karna summons Daisuke to another world, but not as a traditional hero. He is reincarnated as a female adventurer with a specific and disruptive mission. Karna commands Daisuke to infiltrate the party of the local hero and cause its collapse from within, a phenomenon known as a party crash. The goal is to dismantle the hero's group through internal discord and sabotage before they can become a true threat. However, Daisuke quickly discovers that the target heroes are not naive archetypes; they are eccentric and formidable individuals in their own right, making the mission far more complicated than anticipated.

The central character is Daisuke, a reincarnated former corporate employee now navigating a new world and a new identity as a woman. The mastermind is the demon lord Karna, a powerful entity who maintains the persona of an adorable girl and a beloved streamer, using her influence to meddle in the affairs of the other world. The primary setting is a fantasy realm where adventurer parties operate under the guild system, a familiar structure that Daisuke leverages using his hard-won experience from corporate infighting. The conflict stems from the clash between Daisuke's new life as a saboteur and the unexpected complexities of the heroes he is meant to destroy. Instead of finding a simple target, the heroes prove to be quirky, powerful, and not easily manipulated, turning Daisuke's mission into a high-stakes psychological and strategic battle. The narrative focuses on the infiltration process, the attempts to sow discord among the heroes, and the constant risk of Daisuke's cover being blown, all while exploring themes of reincarnation, labor exploitation, and the deconstruction of classic isekai and fantasy tropes.