Elite Special Forces Captain Lee Yoon-ah, who is said to be Korea's nerd. As a soldier to the bone, there was no romance in her life. However, a completely different world unfolds in front of her, who lost her mind after being hit by a shell while dispatched overseas. Being possessed by a romance fantasy novel written by a friend! She also becomes an extra 'Rosalie' who lives a miserable life. Taking a deep breath and shaking her head for a moment, she considers this a battlefield and decides to change her life. "This is a class society." "Because I've experienced enough to get tired of a hierarchical society called the military." "Are you disobeying my orders now?" Captain who conquers the duke with absolute charisma! However, she unintentionally seizes the romance... "Duke, how does it feel to kneel down to the Crown Prince? It's the first time you've kneeled down to anyone other than the Emperor." The original male lead, not the female lead, falls to her knees. Captain, who didn't care about love, can you win this battlefield?