In Season 1, Geon-woo and Woo-jin align with former loan shark President Choi Tae-ho and his ward Cha Hyeon-joo to dismantle Kim Myeong-gil's Smile Capital network. Myeong-gil launches a night raid on Choi's mansion, killing President Choi and injuring Woo-jin, while Cha Hyeon-joo departs. After retreating to the mountains for grueling strength training with Moon Gwang-mu, the duo teams up with chaebol heir Hong Min-beom to intercept Myeong-gil at the docks as he attempts to flee to Vietnam with 80 billion won in gold bars. Myeong-gil is defeated and arrested, and the recovered gold funds President Choi's charitable trust.
Three years later in Season 2, Geon-woo is a WBC champion coached by Woo-jin. Disgraced fighter Im Baek-jeong tries to force Geon-woo into his dark-web IKFC fighting circuit by breaking Woo-jin's hand, hospitalizing Min-beom, and kidnapping Geon-woo's mother. In the finale, Geon-woo adopts a feral, adaptive combat style during a 2-on-2 brawl in an abandoned complex, knocking Baek-jeong unconscious and rescuing his mother.
The Ending Twist: While police transport Baek-jeong to prison, NIS black-ops agents led by Agent Sin-hyeong (Park Seo-joon) stage his execution. Baek-jeong is given a choice to remain legally "dead" and serve as a covert NIS bloodhound to infiltrate a Thai drug cartel or face actual execution, transforming the primary antagonist into an instrument of state intelligence.