Throughout the film, Lee Yoon-hee appears to be an innocent victim drawn into Lim's orbit. In reality, Han Sang-woo and the Public Security Department coerced her into honey-trapping Lim to frame the Special Unit for illegal collusion and treason.
However, Public Security is unaware that the Special Unit's secret internal faction—the legendary "Illang" (Wolf Brigade)—anticipated their plot from the very beginning. Lim is actually an elite operative of Illang. When Sang-woo leads a tactical team to execute Lim and Yoon-hee in the sewers, Lim dons the full Protect Gear armor and annihilates the entire Public Security ambush in a bloodbath, ultimately killing Sang-woo.
The ultimate ideological confrontation occurs between Lim and his commanding officer, Jang Jin-tae. Jin-tae orders Lim to execute Yoon-hee to eliminate all witnesses and seal the Special Unit's clean victory. Defying the wolf pack doctrine, Lim engages Jin-tae in brutal hand-to-hand combat. Acknowledging Lim's indomitable will and brotherhood, Jin-tae relents.
In the film's climax, Lim secretly escorts Yoon-hee and her younger brother to a train station, allowing them to escape safely to start a new life. Lim watches the train depart, choosing to remain behind as a guardian beast who retained his human soul.