Yu Ijin

Yu Ijin is the main protagonist of the Mercenary Enrollment manhwa (Other Name: Teenage Mercenary, Ipak Yongbyeong). The Story starts when Ijin, a young mercenary and victim of a plane crash, goes back to his family after a decade. He tries to be a normal highschool student and protect the family he had not seen in years, but criminals and kidnappers thwart his path.

Appearance
Yu Ijin is a tall, grey haired boy in his teens. Although he is portrayed with a slender build, he is at least as strong as soldiers of the Special Military Force. He currently outclasses everyone in terms of combat skills introduced in the story. In his mercenary days, he wore olive fatigues and a shemagh to conceal his face. He is mainly seen wearing school attire, casual wear and his formal suit (after becoming a bodyguard trainee).

Personality
As a consequence of his grueling training as a mercenary, Ijin is a composed and reserved person who never panics in the face of danger. He is very astute and decisive. Ijin doesn't suffer from PTSD, although he occasionally has nightmares of the plane crash that orphaned him. He slowly learns about the concept of love and affection after reuniting and spending time with his family, which he starts to value more than anything else. After he begins to attend high school, Ijin is able to make friends and frequently joins them to play Legends of League (MOBA) at the internet cafe. He is noted to be inept at video games, but is unusually adept at actual combat.

History
When Ijin was nine, he and his parents were involved in a plane crash. Although Ijin survived, he was orphaned and was stranded from his remaining family. Eventually he was taken in by an unnamed group. Ijin underwent harsh training, and he worked as a mercenary for about eight years, serving in the harshest battlefields across the world.

Later, during a rescue mission, he saved a RoK major named Kang Hamchan, his team and a doctor. Kang Hamchan traced Ijin's family and helped him retire. Ijin underwent a six month orientation from Major Kang to help him adjust to civilian life. He's currently living with his grandfather and his sister in Seoul. Aside from attending Shinan high school, Ijin works as a part time bodyguard at the SW group's security team, along with fellow classmate Koh Sukjoo.

Yu Dayun (Younger Sister)
Ijin is very protective of his younger sister. When he discovered that she was being abused and bullied, Ijin thrashed the bullies and utterly destroyed the reputation of the main culprits by anonymously leaking footage to the media. He does not like any guy approaching Yu Dayun. He views her as a precious piece of his family, which he never got to experience while on the job.

Grandfather
Ijin's grandfather was devastated after learning of the plane crash, and mourned the deaths of his children. Years later, he was relieved to discover that his grandson Ijin was still alive. He learnt to cook and bought Ijin a smartphone. Ijin is very close to his grandfather.

Lieutenant Kang Hamchan
After being rescued by Ijin in the first chapter, Kang has showed care and took care of Ijin. Kang was the one who located Ijin's family, and was more than happy to reunite them. He taught Ijin all the necessary things a teenager must know to fit in, and also protected him like a brother. He always stays in contact with Ijin, even after he left his care.

Kang's military team also saw Ijin like a younger brother and always have his back.

Lt. Kang denied a request to check into Ijin's background from his fiancé, Shin Jiyeh.

Park Yeongchan
A nerd whom is Ijin's benchmate in highschool. He was also victim of bullying, until Ijin stepped in and stopped it from happening. Park is also a Challenger in Legends of League (MOBA), whom also plays with Ijin and his friends.

Lee Jaehyung and Ju Hyeokjin
Two class bullies who used to harass Park Yeongchan. They give up bullying after witnessing Yu Ijin emerge victorious over Kim Kisoo and his gang. Along with Ijin and Yeongchan, they frequent the internet cafe to play video games. When they were kidnapped by the Gosuk High School Gang, Yeongchan summoned Ijin and Sukjoo to take down the gang and save Jaehyung and Hyeokjin.

Cha Dusik
One of the major mafia bosses in Seoul. Cha Dusik was hired by senator Kim Inbae to eliminate Yu Ijin. After being defeated by Ijin, Cha Dusik views him as a worthy opponent. Later, he is surprised when Ijin is able to hack into his system to access incriminating evidence about Kim Inbae's political scandals, and is further surprised when Ijin uses it to secretly destroy the career of the family. Gradually, Cha Dusik and his subordinates become friends with Ijin after the latter saves them from a rival gang.

Koh Sukjoo
They started of in rough terms because Sukjoo was very suspicious of him, checking his background and falsified information. Sukjoo assumed he was in some way, after Yuna. But after Yuna gets kidnapped along with Dayun, both Ijin and Sukjoo had no choice but to work together. After that incident the tension died down and they become trusted friends. Sukjoo drops his suspicions, and is impressed by Ijin's superior combat abilities. Later, the two of them work as part time bodyguards at the SW group, although in different teams.

Shin Yuna
Yuna is a very kind and gentle person. Ijin's grandfather had mentioned that Yuna took care of Dayun when she was in school, but later moved to the United States for her studies. She came back and met Ijin on the first day of her school. She is in the same class as both Sukjoo and Ijin. Just like Sukjoo, she was also initially suspicious of Ijin, but after her rescue, she no longer doubts his trustworthiness. Yuna is surprised when Ijin reveals he was acquainted with her deceased father; Shin Ingook. She is moved to tears when Ijin expresses Ingook's dying regret of not spending enough time with his daughter.

Shin Jiyeh
The director and heiress of the SW group, as well as Yuna's elder cousin. She tried to investigate Yu Ijin after learning of his role in saving Yuna from the kidnappers, although she was shocked that his background was heavily classified by the government. Later, Ijin begins to train with the bodyguards of the SW group. Impressed with his superior abilities, Shin Jiyeh includes him in her personal escort group. Ironically, Shin Jiyeh's fiancee, Lt. Kang Hamchan, is the benefactor of Ijin and the one responsible for classifying Ijin's information. Shin Jiyeh tried to recruit Ijin into her entertainment company as a celebrity, and was annoyed by his blunt refusal. She is amused to learn that Ijin and her fiance are acquainted with one other, although she doesn't know the exact details about it.