In Parasyte: The Grey, Seol Kang-woo is a gangster lackey who teams up with Su-in. Koo Kyo-hwan plays Kang-woo.
Seol Kang-woo works as a lackey of the Mangnani Gang in the Guro area. At the start of the series, Kang-woo was tasked by the gang to kill the boss of the Yeongdeungpo Cheolis, another gang.
Unfortunately, Kang-woo failed and then fled to his hometown of Namil-gun to lay low. In this whole debacle, the Mangnani Gang basically tried to throw Kang-woo away.
Upon coming back home, Kang-woo notices that his elder sister, Seol Kyung-hee, is acting strange and that his younger sister, Jin-hee, is missing.
Investigating the matter results in him finding out that Kyung-hee is now under the control of a parasite. He keeps looking for Jin-hee while on the run.
A coward
Kang-woo’s investigation brings him to Saejin Church, where he finds Jin-hee’s body. An angry Kang-woo attacks a parasite. That day, Su-in saves him.
The two tag along for a while before Su-in is arrested by Jun-kyung. At a time like this, Chul-min seeks to understand Su-in’s side and enlist Kang-woo’s help.
Kang-woo does provide the information that Chul-min needs but opts out of getting involved again.
It’s then that Chul-min points out that Kang-woo is a coward, which is why his gang turned on him, his elder sister has been parasitized, and his younger sister is dead.
Chul-min reminds Kang-woo that he is once again turning his back on someone who saved him by not joining hands with him to rescue Su-in. Kang-woo is then motivated to join Chul-min in this rescue attempt.
Kang-woo’s fate
Even though Kang-woo keeps desiring an easy way out of this parasite mess, he doesn’t leave Su-in’s side till the end.
After finally defeating the leader of parasites from the Saejin Church, Kang-woo leaves his life of crime behind.
He is welcomed into Team Grey by Jun-kyung. He visits Su-in and surprises her by showing her his identity card.
Before parting ways again, he hands Su-in a message from Heidi and reminds her that even she has a place on Team Grey if she wants to join them.
Also Read: Heidi in Parasyte: The Grey explained