Before I Knew It, I Had Stolen the Dark Lord’s Heartjeongsineul charyeosseul ttaen heungmak juguni gamgin huyeotda; 정신을 차렸을 땐 흑막 주군이 감긴 후였다; Before I Knew It, I Had Stolen the Dark Lord's Heart; My Lord Was Already Into Me When I Noticed; By the Time I Woke up, the Dark Lord Had Wound Down; By the Time I Came to My Senses, the Dark Lord Had Wrapped Around Me; 気づいたら黒幕なご主人様の心を奪ってました

Seeing the relationship between Duke Willow, the Sword of the North, and her father who's his guardian knight, Celine has been looking forward to meeting her lord, Damian. However, the Damian she encountered was a skinny, frail boy with a bright smile that belied his Northern Majesty. To fulfil her duty as a guardian knight, she decided to take her lord's side, no matter what kind of person he was. But there's something fishy about this frail boy...