After recovering her memories of her previous life, Shi Qi discovers that she had disguised herself as a man to infiltrate the Cui residence and become an undercover agent planted by Baihua Pavilion. To make matters worse, she has also been bound to the "996 Ultimate Undercover System," accumulated an enormous debt, and must complete missions to awaken the system. During an assassination attempt, she unexpectedly saves the Cui family's Sixth Young Master, earning merit and a reward while attracting scrutiny from various factions. Facing an unreliable superior, a mysterious assassin organization watching her from the shadows, and an identity that could be exposed at any moment, she just wants to keep a low profile, stay alive, and earn enough money to repay her debt. Yet she gradually becomes entangled in an even bigger conspiracy.