A steel briefcase clicks open in a Seoul high-rise, and inside it sits not money — a name. "Kim Shin." The single most lethal weapon the Korean underworld ever forgot how to fear is back, and the organization that rules Asia's criminal empire from the shadows has no idea he is already inside the building. Amur Tigro, the Russian-Korean killer who answers to no one, steps off the plane with only one directive: offer Kim Shin a job. He finds the man in a place no one thought to look — a quiet apartment, a quieter life — and the Ghost of the Battlefield simply says yes .

"Castle" is not a gang. It is a pyramid of absolute power, and its peak is a throne the syndicate's supreme leader Choi Min-wook has occupied for decades, untouchable, surgically precise, a butcher dressed in boardroom wool. Kim Shin has never cared about thrones or territories — his war was always personal. The Seven Fangs of the Triad, Yakuza knife-saints, Russian mafia executioners, the cartel, Iskra, the names pile up like bodies in a hallway and Kim Shin walks through all of them . But every cleared room drags him closer to the truth waiting at the top: to destroy the beast, he may have to become the thing that sits in its chair.

Also known as: 캐슬, Kaeseul, Castle: The Full-Length Version.