Yu Jin, or Jin to his friends, is the main protagonist of the webtoon and the candidate chosen by the King of the Chachaoongs, Jack to become his successor. Jin is a high school student who has been living in the human world when he is attacked by two random strangers. He is rescued by a man who calls himself the Yi-Mae Tal, who wishes to support Jin as the new king. Even so, Jin has no desire to become the next king and wishes to meet with Jack in order to get him to reverse his decision. Now, Jin finds himself in the middle of a conflict between those who side with him and those who want to destroy him and his companions.
Jin is a Korean high school student with red hair and yellow eyes. He is fairly short (170 cm) compared to most of the other characters, but that is due to him being young. On the back of his neck is an insignia which symbolizes that he has been chosen as the next king. It is only visible to other chachaoongs, who are able to sense it due to the energy it gives off.
Awakened: When Yu Jin is in his "awoken" form, he becomes a full-grown man. His hair grows out to nearly touch the ground. Although the top portion is still red, the tips fade to black; interestingly, this is the inverse of Be-Gak. He loses much of his wide-eyed, innocent expression and takes on a harder, edgier look through the face.
Jin is fairly serious; he does not think much about being alone, nor does he ever seem particularly bothered by the oddities of other people. In general, he likes a quiet life and just does not like to be disturbed. Because of this, he is not fond of the idea that so many people are now living in his house, although he tolerates it.
He will fight if provoked, likely due to the fact that he just does whatever is needed or necessary for any situation at hand. He is incredibly straightforward about his thoughts and opinions, and is frequently irritated by the people around him. Even so, he cares very much for others and will not hesitate to help if someone is in trouble.
In several cases, he is shown to be stingy about food and costs. He has noted many times about things being expensive, how Eun-Yul eats so much, and the fact that more and more people are being crammed into his house, requiring him to spend even more on them.
Awakened: Yu-Jin becomes much more assertive and confident, when awakened. His sense of justice drastically increases and he is far more ruthless when dealing with enemies. That said, he still stringently adheres to Jack's law and tries to avoid killing others, regardless of their actions. He behaves as if he is an entirely different person than his teenage self and is intentionally continuing to conceal himself. Although he recognizes the people he is dealing with, hints about past encounters with them, and speaks to them as if he knows them, none of them recognize him in his teenage form, even though they all feel he seems "familiar".
Although it is a fairly new ability, Jin has managed to materialize a few weapons as characteristic of all chachaoongs. His awoken form seems to favor fusion similar to Yi-Mae.
Also similar to Yi-Mae, he is shown to be able to regrow his arm even after it is viciously ripped apart by another chachaoong, an ability most have never seen before.
He is also rather confident in his speed, when in his awoken form, explicitly stating this himself.
- Li Nae Mee - She is Jin's human friend and classmate who often comes knocking on his door to go shopping.
- Yi-Mae - He is the one who reveals what chachaoongs are to Jin as well as protects him from attacks from other chachaoongs. Yi-Mae describes their relationship as master and subordinate.
- Mu-Young - He likes to think of himself as like a father to Jin. He has known the boy the longest, both having met one another as "humans". Mu-Young will do anything to protect Jin. If it were not for Jin, Mu-Young would still not care nor want anything to do with the chachaoong world.
- Eun-Yul - The owner of the Baek-Jung Tal is tricked into nearly killing Jin before he is stopped by Yi-Mae. Since that time, Jin and Eun-Yul have developed somewhat of a brotherly relationship. They frequently pick on and torment each other, but seem to have become close friends despite the initial animosity between them.
- Ara - Yu Jin is largely indifferent to Ara's amorous advances, but she tends to inform everyone that they are engaged regardless of his wishes.
- When the mark first appeared on Jin's neck, all other chachaoongs felt it due to the energy, or aura, it emits.
- One of Jin's hobbies is making really bizarre combinations of food. He seems to be aware that they actually taste pretty terrible.
- Jin has decided that one of his goals in life is to make something Baek-Jong is not able to eat.
- Yu-Jin hates things related to the paranormal but can't identify why and feels almost as if the idea was 'planted' in him at some point in the past.
- Is an impulse shopper, as demonstrated several times (though he seems to also feel buyer's remorse when he does so).
- Has deadly aim when throwing things--particularly when angry. Also states he will throw anything in hand, even if it's a knife.
As far as Yu-Jin remembers, he was raised by someone he referred to as "Granny," but who passed away, just prior to the start of the story. He still lives in her old house and attends high school like any normal Korean kid, although, his work load is significantly greater than most students, as he has to both study and take care of himself. Beyond that, not much is known about his childhood besides that he met and developed a close relationship with Mu Young at some point in the past. He had nothing to do with the Chachaoong society and didn't know of his true origins until he met Ei-Mae.
There have been many hints that Yu Jin's past, and connections to the Chachaoong are far more complex than he knows, as evidenced by obvious deeper connections to Chachaoong like Ei-Mae, Bi Gak and Eun Yul. His reason for hiding, and his true identity are, as of yet, unknown in the English version.
(Major spoilers beyond this point)
When TAL begins, Yu Jin is a normal high school student who dislikes paranormal topics and has normal, human friends. His life changes dramatically when he is attacked by two chachaoongs on the street, then rescued by a masked guy in a hanbok named Yi-Mae. After being told that he is the second generation king, Jin becomes determined to locate Jack and find some way to step down from his position. This refusal to take the throne caused wide spread frustration in the chachaoong community, as Jack's power is dwindling (strong nonetheless) and the second generation cannot begin properly until Jin becomes king. Already frustrated that a "no-name" was declared king, instead of the one everyone expected, the fact that Yu-Jin is ignoring his responsibility has further frustrated those in the chachaoong community.
After the first attack, Yi-Mae moved in with Yu Jin to function as his primary body guard. Mu Young, a long time friend of Yu Jin's returned from overseas travel, and was astonished to learn that not only was Yu Jin a Chachaoong, also a the second generation king, no less. He also decided to stick close to Yu Jin in order to keep the boy safe, as he did not trust Ei-Mae. In order to hide his aura and make it easier for him to move around without being detected, Ei-Mae gave Yu Jin a specially created bandage to cover the insignia on his neck. Unfortunately, this has been only marginally successful in protecting Yu Jin.
He was found and attacked shortly after, by Baek Jeong, who was vastly disappointed in his fighting abilities. Baek Jong would have killed him not for the fact that Yu Jin briefly awoke and fought back. Baek Jeong was startled when Yu Jin suddenly referred to him by his name, Eun Yul, since Ei Mae was previously the only male chachaoong to do so. Mu Young and Ei Mae broke into the fight and Baek Jeong realized he'd been manipulated into attacking Yu Jin. Baek Jeong invited himself to stay at Yu Jin's place--the second of the Tals to start living there--though this was largely due to the presence of Ei Mae than any real desire to be near the king.
Yu Jin was surprisingly tolerant of having Eun Yul at his place beyond complaining of another mouth to feed, as Eun Yul is a glutton, and noted to be a free-loader. Especially considering that Eun Yul made it a point to bully the "newbie king" at every available opportunity.
Shortly after Eun Yul's arrival, Yu Jin out with a friend, and was spotted by Ara. She took an immediate interest in him and stalked Yu Jin back to his house where she immediately began flirting and declaring her love for him. Yu-Jin was not particularly enthused with her advances, to the point of referring to them as sexual harassment. Nevertheless, he made little effort to force Ara to leave when she took up residence in his house (though it could have been because Ara is noted to be the strongest of the Tals when it comes to sheer physical strength). Ha Na Rin arrived the next day, having stalked Ara there.
When Yu Jin was not receptive to her staying there as well, Ha Na Rin offered to read his fortune for him as payment, but realized his past and future were both completely shrouded from her power, something Yi-Mae was glad to hear.
With four eccentric Tals at his house, Yu Jin tried his best to balance a normal school life with the new found weirdness at home and generally coping with being a reluctant king. But Yu Jin continued to be targeted by others, and soon encountered a clumsy young chachaoong who stalked him to and from school several times with the intentions of attacking him. Fortunately, Jena's abysmal fighting skills posed no real threat, and with Ei Mae's help, Yu Jin was able to confront her to find out that Ja Gwi was behind everything, including the recent attack on Mu-Young. After hearing the tragic story of Jena's family and how they were being forced to work for Ja Gwi, Yu Jin offered to help set the three of them free. He extended this offer to Hiljo personally, promising that Ei Mae would remove the marks on their bodies, by which Ja Gwi controlled them.
However, Ja Gwi confronted the group and murdered Hil Jo before Yu Jin could free them. Yu Jin was traumatized by watching someone die in front of him, and moved into a fully awakened state. This was the first time his appearance completely changed--he appeared to grow taller, as his school uniform fit tighter on him, and his hair became extremely long, fading to black toward the ends. In this state, Yu Jin had a much more imposing demeanor, and appeared to know far more about his situation than his usual self. Though he refused to kill Ja Gwi, he did injure him, removing the arm that was used to place marks on young Chachaoong. Before reverting back to his normal state, he also told Ei Mae to not get involved with Bi Gak.
It was after this incident that Yu Jin began having difficulty with his vision, worrying everyone. After Human doctors could find nothing wrong with his eyes, the Tals decided to locate Sae Ha, one of few chachaoong doctors (and a Tal, at that). Sae Ha was summarily located and brought back to Yu Jin's house. His assessment of Yu Jin's eyes was that it had to do with Yu Jin using his abilities to change his appearance. Yu Jin denied that this was the case, and claimed to have no knowledge of how to do this in the first place. Though Sae Ha was doubtful, he assured Yu Jin that his vision should return to normal soon and prepared to leave. But upon realizing that Ah Ra was living with Yu Jin, sae Ha stated that the latter's condition was very serious and he would have to stay to keep an eye on his situation, thus becoming the fifth Tal to live with Yu Jin.
Yu Jin played a largely tertiary role in Mu-Young's arc though he was nearly devastated when it seemed Mu Young would die from Leon's venom. Even his awakened self was determined not to let Mu Young die. And when Chuh-Yong finally forced a confrontation between the twins, an awakened Yu Jin showed up with Ei Mae to stop him from killing Ignatio. Chuh-Yong made it very clear that he does not like Yu Jin and loathes him for refusing to take the throne. He would have fought him then and there, if not for the fact that Jack wordlessly intervened. After shooting Yu Jin an unfriendly glare, Jack and Chuh-Yong retreated, letting Ignatio live and Yu Jin return to his normal life.
Currently, in the English translation, Yu Jin continues to live with the five Tals, and receives frequent visits from Mu Young and Ignatio. He has met Cho Yi, another Tal who works nearby, and seems no closer to accepting the title of king than he was at the start.
Recent Korean chapters have revealed that Yu-Jin is actually the real Yi-Mae and that Yi-Mae shown until this point is his yongma. It is still unknown why they both have been disguised.