Changho seo

Appearing in s2, ep.186. He is the action squad leader. His prison number is 5090.

He attends a meeting of the best managers. After its conclusion, he was unsatisfied of Yungyeol's leading direction and wants to destroy TRPA soon ordered by Gyocheol. He challenge Yungyeol's position but was shut down by Mari as she dislikes his whining and tells him she will do it. Later, while on his motorcycle, sees Mari's plan not working and confronts about it but sees her next set of plans to be working.

Back at HQ, he was at the pool with Mari realxing but exits the pool as he thinks she is undeestimating the TPRA. When the challenge was soon defeated due to TRPA and their allies, he questions Mari of if she has more plans but is confused she doesn't. In the midst, he taunted Hwajin to come to the HQ as a way for him to defeat Hwajin with numbers. In addition of kidnapping Dongcheol Go's son. He was arrogantly confident but failed to see Hwajin's superior fighting prowess. However, when that failed, he uses Minseo Go as a hostage but Hwajin only responds by pulling out a gun.

Changho was confused if it was real but ignores it. In a split moment, Hwajin throws the gun at him, disloding him from Minseo. Then both fistfights with Changho arrogantly and underestimates Hwajin which led him to be beaten to unconsciousness. Soon, he wakes up and is confronted by Hwajin again. He was forced to reveal more of Gyucheol's obession and want of Gayoon. He then wouldn't snitch on his own group but was going to reveal only the name of the second in command when the police and arrested him. He confessed to the police but deny involvement of the TRPA challenge. He instead reveals Mari and Yungyeol's involvment but the police didn't believe him and is waiting for his trial.

He is seen imprisoned at Gimcheon Detention and meets Gyucheol and Jonghyuk. He tells them of Yungyeol's betrayal. Gyucheol demands what of the progess of killing Hwajin but Changho explains it is abandoned since Yungyeol is now effectively the leader.