"Rule Number One: Don't wake me up unless we are under fire." Kang Jin-Woo, codename: GHOST. Former Status: The world’s number one assassin. Current Status: A minimum-wage waiter who just wants to play video games and sleep. But when he casually dismantles a hit squad sent for Park Seo-Yeon, the cold-hearted queen of the business world, his retirement is violently cancelled. Forced into a staggering contract, Jin-Woo becomes the live-in guardian for the three heirs of the Park Empire: * The CEO (Seo-Yeon): An ice queen with a terrifying secret—a second, seductive personality that awakens when her heart races. * The Idol (Ji-Eun): National superstar, energetic troublemaker, and master of teasing. * The Gamer (Min-Ji): A cynical hacker who prefers virtual reality to the real world. Moved from a cramped one-room apartment to a sprawling Gangnam penthouse, Jin-Woo has to navigate corporate warfare, obsessed fans, and an unseen villain manipulating their lives from the shadows. But the biggest threat isn't outside the penthouse. It's inside. As the sisters uncover the scars of his past, their curiosity turns into obsession. In a house full of Korea's most desirable women, all vying for the attention of their stoic protector, Jin-Woo realizes that surviving the battlefield was easy—surviving this penthouse might kill him.