Main characters
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- Sa Ghang Gwon
Sa Ghang Gwon is a Trace with the ability to manipulate ice. His powers had been with him since his birth, and because he could not control them, Ghang Gwon accidentally attacked his own parents. With no cure or solution to Traces, his parents abandoned him on a street next to an old beggar woman Trace who could conjure fire. He wandered around for an indeterminable amount of time, living his life as a scavenger and losing his emotions. He engaged in battle with his first Trouble, but after realizing he could not defeat it, he encased himself in ice until it disappeared. He passed out in a park, where he was found by Han Tae Eun. She took him home and asked her father if she could keep him. Afterward Tae Eun called Ghang Gwon her possession. Her family, consisting of only her and her father, adopted him, but Ghang Gwon, fearing that they would abandon him like his parents, hid from them his identity as a Trace. Over the years, he continued to battle Troubles, honing his skills. Whenever he is injured, though, he lets Tae Eun believe that he was bullied by his classmates.
When a Trouble attacks his class, Ghang Gwon attempts to come to the rescue, but Tae Eun stops him, knowing that if he fights the Trouble, his identity as a Trace will be revealed. She begs him not to get involved, but Ghang Gwon engages the Trouble and defeats it. Afterwards, he is taken by the government for three months, and then enrolled in a Trace school. His prime objective is to leave the Trace school and return to his family as soon as possible, and he believes that capturing the Beggar Team will grant him freedom.
Ghang Gwon is very quiet and almost antisocial. He hates that he is a Trace, shamefully hiding it from Han Tae Eun and her father; often, he mutters to himself that he is not a Trace. But he also specifically uses his powers to battle and destroy Troubles, so that his family can be safe. He is easily bullied and also submits to their beatings without complaint (for the sake of Han Tae Eun's safety), which only angers her. He has no facial expressions and seems to enjoy antagonizing her, calling her "battle addict" or "fighting chicken." He is extremely protective of her and her father, as his family. He seems to find Tae Eun especially precious. It is hinted that he likes her as more than a sister; while in the Trace academy, he repeatedly writes letters to her, ending each with the words "I miss you."
- Han Tae Eun
Hot-blooded and fiery, Han Tae Eun is well known in her school as a formidable fighter, more inclined to her fists than talking things through. She yells often, especially at Sa Ghang Gwon when he aggravates her. As a child her mother was killed by a rogue Trace in a park, and Tae Eun repeatedly visited the same spot her mother died, until she found a barely conscious Sa Ghang Gwon lying there. She took him home and adopted him as her possession. At some point in time, she discovered he was a Trace and labored to protect his identity, unbeknownst to him.
When Sa Ghang Gwon is taken away by the government, Han Tae Eun declares that she will become a Trace and be like him. She repeatedly battles Troubles at the expense of her own life, but then she awakens as a Trace. Her arms turn a sparkling red and shoot sparks, granting her inhuman strength and abilities. It seems that she needs to repeatedly punch hard objects like the ground to activate one of her arms, but if she strikes her fists together, the other arm will ignite.
Tae Eun is easily angered and irritable but also fiercely protective of Sa Ghang Gwon. She protects him specifically to prevent him from fighting back, so that he won't accidentally reveal his identity as a Trace. She seemed to resent that he was a Trace while she wasn't and accused Ghang Gwon of the same feelings, since he tried to hide his true identity from her. She's stubborn, believing that if she fought Troubles, she would become a Trace. After she becomes one, she goes about fighting Troubles, in the same way Ghang Gwon did (dressed with a face mask). Tae Eun seems to hold romantic feelings for Ghang Gwon, getting jealous when he carries Se Yeon and tells Tae Eun to run while escaping a Trouble.
- Kim Yoon Seong
Kim Yoon Seong was a man with a perfect life: a job, a loving wife, and a daughter. All this changes when one day he turns into a trace. Being a law-abiding citizen, he decides to legally register as a trace, rather than hide his identity. After that he is separated from his family who are taken to a trace facility where the family of the traces are taken. When he is not able to contact them he goes to the facility to see his family where he is stopped by a group of trace guards and chased where he meets Jeong Hee Sub who is also a trace trying to get into the facility. They join and form a team and recruit other members. They succeed in entering the facility where Kim Yun Seong finds the family of the traces who are brought there are used for experimental purposes and killed.
- Morrienoah Jin
As a child, Jin was an emotionless trace who had ideals that 'The good should live, the bad should die', killing people who he deemed as bad. After coincidentally saving Morrie, he was raised by him to become a killer. He easily obtained the top title of Morrienoah that every killer wanted, being described as the perfect killer as he had no emotional weaknesses. This changed when he received a bizarre contract to protect a girl named Jang Mi (Rose) for a month from a killer. Rose gradually changed his life and Jin fell in love with her as the deadline drew closer. Jin managed to kill the killer after her life, yet, she committed suicide in front of him shortly after. Turns out that Rose was one of his victim's child and swore revenge by giving him love and make him lose it. Despite all that, she truly did love Jin. Jin was recruited into the 'Pierrot team' to infiltrate the facility much later in life.
