it turns out Seong Hun and Jay have been working behind the scenes with Jin Wook to uncover the truth about Ji Won’s disappearance. Jin Wook met them in secret and insisted he isn’t the culprit. To prove his innocence, he shows them security footage from the gym, where he was during the time of the murder. However, Jin Wook recalls receiving a call from Jin Uk, the victim, and rushing to their meeting spot—only to find Jin Uk dead.
Suddenly, someone strikes Jin Wook from behind, knocking him unconscious. When he wakes, he finds a bloody sickle in his hand. Panicked, he hides the weapon in a storage room but has since been blackmailed by the true killer, who is framing him for the crime.
Seong Hun, Jay, and Jin Wook realize the culprit must be someone from their inner circle. All signs point to Seung Hui. They bring Gi Hyun into their plan, pretending to spy on Jin Wook but actually monitoring Seung Hui. Gi Hyun follows Seung Hui but it all ends up at a dead end. Suspicion grows as Seung Hui and Gi Hyun leave together, leaving the trio to question their next move. Jay remains convinced Seung Hui is dangerous and fears for Gi Hyun’s safety.
Later that night, Gi Hyun arrives home while talking to his mother on the phone. He is startled to find Seung Hui waiting for him outside his apartment. By morning, Gi Hyun is missing. His phone is off, and no one can reach him. Seong Hun, Jay, and Jin Wook launch a frantic search. Jay checks a tracking device he Gi Hyun had encouraged them to have and discovers his location—an abandoned site where they once held a volunteer program.
They rush there and find Gi Hyun unconscious. After waking him, Gi Hyun warns that Ji Won is in grave danger. Jin Wook stays behind to help Gi Hyun recover, while Seong Hun and Jay head off to rescue Ji Won. Despite his fear, Jay is reassured by Seong Hun.
They find Ji Won tied up and gagged. Before Jay can fully free her, Seung Hui appears and coldly confesses to the crime. As Jay pulls the tape from Ji Won’s mouth, she urgently warns Seong Hun to watch out. Seong Hun is struck from behind with a shovel, collapsing. The attacker is revealed to be Gi Hyun, leaving Jay in shock.
Ji Won, Jay, Seong Hun, and Jin Wook are bound together. Gi Hyun and Seung Hui smugly explain their plan. Gi Hyun reveals how everything spiraled out of control. Jin Uk had confessed his love to Jin Wook but was rejected. Later, Seung Hui tried to comfort Jin Uk and confessed his own feelings but was also rejected harshly by him.
In a fit of rage, Seung Hui and Jin Uk fought, and Jin Uk accidentally fell onto a sickle. Seung Hui fled, but Gi Hyun, remorselessly smothered Jin Uk to ensure he wouldn’t survive. They framed Jin Wook by using Jin Uk’s phone to lure him to the scene and knocking him unconscious.
The pair taunt their captives, planning to stage their deaths as accidents. Gi Hyun douses them in gasoline, but when he realizes Seung Hui is filming the entire scene to upload for internet fame, they argue. Their distraction allows the others to free themselves.
A fierce fight breaks out. Gi Hyun lunges at Jay with a knife, but Seong Hun takes the hit to protect him. Jin Wook overpowers Gi Hyun, while Seung Hui, still filming, tries to escape.
In the aftermath, Gi Hyun and Seung Hui are publicly exposed and arrested. The news of their crimes shocks the community.
Two months later, life returns to normal. Jin Wook mentors Ji Won in fitness training. Seong Hun and Jay, who earned top marks on their fitness tests, continue working out together. Their relationship blossoms, culminating in a kiss at the gym as the series ends on a hopeful note.
