- Mr Yi: Nothing is known about his relationship with his father as they were never seen together.
- Mrs Yi: Shi-Woon's mother, she is commonly absent as she works, but she cares greatly about her only son despite not being able to spend a lot of time with him. Shi-Woon holds great care for his mother, as after seeing what the S.U.C. had done, he resorted to denying his master's words to leave the Murim in order to get stronger for revenge. He was so angry that Gyu-Bum Yi compared his expression to that of Chun Woo the day that Shi-Ho was shot. Also, due to his anger he had killing intent while in a mere sparing with Elder Jang-Il Jeong much to the later surprise. When he learned that there is a possibility that So-Chun Hyuk could be part of the S.U.C and he tried to use the meditation training in order to fight him and couldn't lay a finger on him he almost gave up. However, remembering the condition his mother was in he regain his will and determination to fight even if it cost him his life. This determination was so strong to the point of Hyuk felt it by feeling weird for a moment despite the distance between them. Recently after the event of Seoul tower Shi-Woon was shown to be depressed, but hearing that his mother woken up cheered him and he was seen smiling after days of depression.
One of his closest relationships is his teacher, who had been the core of power that literally not only changed, but shifted the course of Shi-Woon's life.
- Jang-Il Jeong: An elder of the Sun-Woo Clan, he originally didn't think much of Shi-Woon, but, after taking him as his martial arts student, Jang-Il has been considerably impressed by Shi-Woon's incredible willpower. His death caused Shi-Woon's rage, that resulted in him getting in the Black Origin Threshold, and he was the one to pull Shi-Woon out of it. After his death, Shi-Woon believes he is the reason he still lives on.
- Yae-Won: During his protection by the Mil-Yang Clan Shi-Woon received lessons on meditation by Elder Yea-Won. According to her, if one does not keep using the Ki with that kind of training then the Ki becomes useless even if the Ki center is fixed. She also believe that if Chun-Woo had his way in training Shi-Woon he would have turned him into a true monster. She state that she want to help Shi-Woon retain his martial arts in order to help him break the chains of ill-fate which he inherited from and binds his master Chun-Woo who inherited it from his master Un-Wol to the Murim.
Friends and AcquaintancesEdit
- Jang Joonho: Indebted towards Shi-Woon for saving his older brother from Goomoonryong. He helped Shi-Woon by warning him about other schools that could come after him and aided him when he faced Chang-ho who tried to attack him during the time his Ki Center was broken.
- Mun-Gi Ma: A member of the Four Supernovas. He was Indebted towards Shi-Woon for asking Chun-Woo Han not to kill him but to spare his life after their fight.
- Shi-Ho Lee: A medical practitioner of the Murim and former love interest of Shi-Woon's former master, Ms. Lee first introduced the One Moon Divine Medicine to him in order for the former to better adjust his body so he could better practice martial arts. In a sense she's as much a guiding factor in changing Shi-Woon's life as much as the Goomoonryong. Like many of Chun-Woo's associates he was also devastated when Shi-Ho had died during the final bouts in the initial series, but was humorously perturbed when she thought he'd be fun to play with when he got older, brushing off this premonition as coming down with something.
- Gyu-Bum Yi: A retainer of the Sun-Woo Clan and a member of the Four Supernovas. At first he was an enemy due to his work at the MAA. However, after learning that So-Sul was freed and that Shi-Woon helped in it he helped him back and after So-Sul gave the order to support and protect Shi-Woon and appointed him as her temporally replacement until her return Gyu-Bum became loyal to Shi-Woon.
- Ji-Gun Yoo: A former enemy of Shi-Woon due to believing Shi-Woon was a member of the S.U.C. After the his defeat and clearing of the misunderstanding the two eventually became friends and helped each other back-to-back.
- Jung Lae Won : Shi-Woon saved him from his Police Chief when he was about to kill him.
- Ryuji : A former member of SUC who fought and tried to kill him once during invasion of Nine Dragon school. Ryuji, after he found out what he wanted from Chun-Woo, went and revealed Chun-Woo's plan to take over of Seoul
- So-Chun Hyuk: A former enemy of Shi-Woon, they were eventually led to a mutual agreement and respect in which being enemies in no more. Shi-Woon is the basis of Hyuk So-Chun's thoughts in life as of now, for his knack of courage had shocked him. Currently Shi-Woon sees So-Chun Hyuk as a rival whom he wish to supass him one day.
Allied Schools and ClansEdit
- Mil-Yang Clan: After the suspicion that Shi-Woon is part of the S.U.C. was cleared up, Sera Kang became friends with Shi-Woon and romantically attracted to him resulting in an allied relationship between the Mil-Yang and Sun-Woo clans.
- One Moon School: After Hyun Won-Jae unknowingly became an accomplice in Shi-Woon's kidnapping by Seung-Jae Bae he committed to fix Shi-Woon's Ki center which brought the One Moon School and Sun-Woo Clan under a cooperating situation. Since then the OM School and SW Clan seem to communicate frequently.
- Shinhyup Clan: As the clan that Ji-Gun Yoo formed to fight the S.U.C. it fought alongside the Sun Woo Clan against S.U.C. and since the leaders, Shi-Woon and Ji-Gun are friends and allies the two clans are allied as well.
- Martial Arts Alliance:
- Sae-Hee: From the beginning the two seem to care about each other but none of the two has expressed romantic feelings thus far. In a conversation between So-Sul and Shi-Woon, the latter didn't deny that Sae-Hee was his girlfriend but he did not show jealousy towards Ji-Gun's flirting behavior. Another prove could be that he only refers Sae-Hee to be a precious friend of him when others are asking for their relationship (e.g. season 2, chap. 12). This makes the belief of romance between them uncertain and suggests that the reference to Sae-Hee as "girlfriend" could also refer to "a friend who is female". It is also possible that this word has no romantic meanings to Shi-Woon because he didn't try to correct Seung-Jae Bae who thought Jin-le was his girlfriend.
- Jang So-Sul: His carefree/absent-minded nature as well as the fact he saved her in a time of strife has caused So-Sul to develop an interest in Shi-Woon and tries futilely to hide it. She is shown to be protective of him, even go so far as to mobilize the entire Sun-Woo Clan against Chundo-Moon and forcing Alex to take her in helicopter to the Koa tower in order to save him. She also ordered Gyu-Bum to assist and protect him until she returns as she appointed him her replacement as the head of the Sun-Woo Clan. It is also explained by Shi-Ho that the true reason for her to join the Black Forest Defense is to cure her condition so she can properly grow and get a boyfriend like any normal girl.
- Jin-Ie Kwon: As Shi-Woon's bodyguard who was assigned to him by the Sun-Woo Clan, she has spent considerable time with Shi-Woon and eventually developed some feelings for him. When her grandfather ordered her to kill Shi-Woon while he was unconscious, Jin-Ie found herself conflicted between her feelings for him and her desire to maintain a bond with her grandfather, and was rendered unable to kill Shi-Woon. When Shi-Woon learned about a skirmish between Jin-Ie and the S.U.C, he decided to stall his training and go out of his way to save her. The result of that event has led to her increased affection towards him as well as the approval of her grandfather. She has also developed a very protective nature towards Shi-Woon due to her deep feelings for him. After the attack on Shi-Woon school and him being missing she called Sera and stated that she would if Sera won't find him she would even if it cost her her own life.
- Sera Kang: Despite seemingly being an enemy of Shi-Woon, in recent chapters Sera often puts him in awkward situations, such as when she gets unnecessarily close or gropes him; she has even mentioned that, if ordered by the Sun-Woo Clan, she would do "nightly service" for him. While Sera Kang appears to be the cold, business-like type, interactions with Shi-Woon have caused her to act unbecoming of her such as smiling or blushing. She has also shown in recent chapters that she is attracted to him because of his protective nature to the people he cares for.
He has had several enemies to have crossed with, some more critical than others.
- Chun-Woo Han: Shi-Woon's former master and English teacher of Nine Dragons High School. Shi-Woon showed great devotion for his master who also showed that he care greatly for Shi-Woon as showed when Shi-Woon confronted Hyuk from the Heavenly Way School he refused to believe what was said about his master or give any information on where he is, Chun-Woo, who considered leaving Shi-Woon behind due to the power of the Heavenly Way Clan, went to his rescue. At the end of Part 1 Shi-Woon devotion for his master managed to awake him from the Black Origin Threshold and Chun-Woo tried to give his disciple his normal life by expelling him, breaking his Ki Center and state that he was just a toy he was playing with. However, After the event of Part 1 of The Breaker, Chun-Woo greatly changed. He no longer care, threaten to kill and even attempted to strike his former disciple when he called him master. Despite this Shi-Woon devotion for his master never changed and when he was asked if he could go against his master, he didn't answer. However, after hearing Kang-Sang reason for attempting to stop Chun-Woo, Shi-Woon decided to stop his master himself. After that when Shi-Woon was questioned many times if he is certain that he is able to convince his former master to stop he always confirmed it and Chun-Woo himself started to remember part of his past and questions if he ever had a disciple. After remembering Shi-Woon name Chun-Woo still can't concentrate and remember who he is and every time he trys to he started to get a severe headache. When the two confronted each other again, after Shi-Woon learned of the scheme against the Murim and the intention to frame his former master, Chun-Woo questions who is Shi-Woon and why whenever he sees him he is worried about his well-being. After the failed attempt on Chun-Woo life he managed to regain his memories. However, after Chun-Woo regained his memories and seeing Shi-Woon there he angrily ask his former disciple why he is there and once again disown him and tell him that whatever relationship between them as master and discipline is over. Shi-Woon still tried to stop his master and prove that he is worthy of being his disciple. Seeing that Shi-Woon is telling him not to press the button of detentions and Jung Chan is telling him to press he had them fight for that. Shi-Woon loyalty to his master was proven to be so strong to the point that Elder Kwon stated that Shi-Woon holds his master higher than his own life as he saw Shi-Woon trying to stop his master and asking him to take him back as his disciple again. However, when Elder Kwon saw that Shi-Woon is willing to aid Chun-Woo to escape from the Alliance without having him to press the detonator he concludes that Shi-Woon is trapped in the shadow of his master and decide to stop that by ignoring the order of stand down, fighting the Nine Arts Dragon and allowing his opponent to kill him. This seemingly shattered Chun-Woo and Shi-Woon relationship as master and disciple. After Shi-Woon uses the Cry of the Phoenix Chun-Woo goes to him and try to calm him down. Shi-Woon recalled all that happened since he meet Chun-Woo and after he had left, states that he can no longer believe in his former master, attacked him and called him by his title as the Nine Arts Dragon instead of teacher with an angry expression with tears streaming from his eyes and in the same manner as Chun-Woo Han's enemies. This indicates that Shi-Woon now sees his former master in the same regard as the Martial Arts Alliance and that he had finally given up on Chun-Woo Han altogether. However, Ju Sang-Sik noticed that Shi-Woon missed six times to kill his former master despite having the power and the chance to do it. It also seem that Chun-Woo was hiding the existence of Shi-Woon from Kaiser as Kaiser seem to have figured this out as he called Shi-Woon a hidden treasure. However, Chun-Woo stopped holding back, break both of the arms and legs of Shi-Woon then step on his head and tell him that he doesn't plan on being defeated by a weakling like Shi-Woon When asked by Kang-Sung if he really intending on killing his only disciple he reply with reminding him the Shi-Woon is no longer his disciple hinting that he has completely forsaken Shi-Woon just like Shi-Woon no longer believe in Chun-Woo by now. Chun-Woo had even used Shi-Woon as a bargaining tool to obtain the helicopter the elders were in at that time as well. Though while escaping in the helicopter he had silently contemplated Shi-Woon in the entire fight and prayed that Shi-Woon would eventually catch up to his level and displayed happiness at that thought as well as the time they spent together as master and disciple. This implies that Chun-Woo had threatened Shi-Woon's life earlier in an attempt to drive Kaiser's attention away from his former disciple as he had figured out that Kaiser and his associates were watching the entire fight when Elder Kwon revealed that the detonator he held would blow up the park they were in.
- Kaiser: As the leader of the Black Forest Defence he is an enemy to the whole Murim. Kaiser become interested in Shi-Woon after witnessing him using the Black Origin Threshold and fight against Chun-Woo. Labelling him as greater "Demon King" than his former master. Later he order Jae-gal to assassinate Shi-Woon just to see if he was worthy of himself.
- Soldiers Under Command: They are Shi-Woon's sworn enemy, as he is the only true disciple of Goomoonryong, he is a threat to their organization and thus their biggest target.
- So Jung Chan: as the commander of the S.U.C., his priority is to destroy any evidence of the true relationship between them and the Nine Arts Dragon including killing his previous desciples.
- Jae-gal: as the right hand of the S.U.C. he role is to follow his commander's wishes.
- 5 Captains: As the five captains of the supposed disciples of Nine Arts Dragon, they fear Shi-Woon's knowledge of their teacher and after failing to recruit him they repeatedly tried to kill him.
- Chang-ho: Shi-Woon was originally a victim of Chang-Ho's bullying, and that alone caused a lot of resentment towards Chang-Ho. He would often make threats about Sae-Hee, which in turn caused Shi-Woon to eventually confront him. As Chang-ho became a part of the S.U.C. they continued clashing with more aggression coming from Chang-ho rather than Shi-Woon seeing him as an enemy.
- Rival Schools: As the disciple of the infamous Goomoonryong who killed their Munju, Shi-Woon is subjected to the vengeance of many Martial Artists Schools including: