Hak was adopted by Son Mundok as an orphan and they share a caring, casual relationship. Hak refuses to call Mundok “Grandpa” and also refuses to hug him when they see each other, believing that he is already too old to be doing such things. However, when Hak is being disrespectful, especially to the royal family, he is not spared from Mundok’s discipline. Mundok cares greatly about Hak will defend and protect him in any situation and even cried when Hak decided to leave the Wind Tribe and no longer be their general after he was falsely accused of murder.
Hak shares a close friendship with Yona, and they often playfully bicker with each other. He feels extremely protective of Yona, both on a physical and emotional level, and enjoys teasing her. He has been in love with her since before the start of the series since childhood but has grown to suppress his desire of doing anything outside their friendship because of her feelings for Soo-Won. After they become fugitives, Yona asks that he call her “Princess” to retain who she once was and he accepts her request with no hesitation. Jae-Ha questions his relationship with Yona often, poking fun at him any chance he gets. After the princess's risky mission, Hak tends to Yona's injuries by pouring honey on her hands, which had splinters in them from collecting the medicinal Senjuso plant, and zones out, thinking of what Jae-Ha had said, spilling the honey all over them. Taking one, he starts licking off the excess. Embarrassed and confused, Yona runs away and Hak is left questioning himself.
Because of his oath to King Il to protect her, he considers himself a tool for her to use and will do anything for her sake. For this reason, he fears for Yona's safety whenever she does reckless things, at one point stating that he wants to ‘tie her down’ so that he can stop her. However, he is also excited to see her finish the risky things she gets herself into because he wants to see her struggle like a normal, ordinary human being, which is something she was unable to do previously, due to her lifestyle. Although some may believe he wants to keep Yona hidden, he, in reality, wants to show her off to everyone, especially the people who chased her out of the castle, so that he can tell them how fine a princess she has become.
In chapter 134, when they go to Kouka in hopes of negotiating with Soo-Won to stop the threat of war, an overly-stressed Yona worries herself to the point of hyperventilation and faints. Later that night in their tent, Hak tries to make her feel better about the current situation of the Four Dragons but is surprised when she comforts him. Touched, Hak embraces her tightly and confesses his feelings for her. Unfortunately, because his voice was muffled, Yona didn't comprehend what he said, only catching the tail-end of it. When she asks Hak to repeat his sentence, he lets go of her, embarrassed for almost spilling his secret. The next morning, Yona wakes up recalling that in her dream Hak had told her something important. Additionally, in chapter 137, they're about to split up to find aid to delay the impending war. Seeing Hak's anxious expression, Yona reaches up and pulls Hak into a kiss, leaving shortly thereafter. Hak, having dealt with an unrequited love for years, is unequipped to deal with this new development, and is teased by Ogi. He is in turmoil, wondering if the princess had real feelings behind it, but ultimately deciding to push the thoughts aside until after the Xing conflict is resolved.
Then in chapter 151, it's revealed to Yona through eavesdropping that Hak has a fiance (Ayame) in the Wind Tribe that had been arranged by Mundok during his childhood. This prompts her to decide to tell him he is free to go back to them if he wanted to. Having taken this as an expression that he's no longer needed, Hak becomes visibly upset and distant from Yona, though he does decide to stay regardless. After swift intervention from the others, Yona quickly realizes her mistake and asks him to stay. Annoyed that she'd think he would leave, he tells her he is following her because he wants to and states that his home is among the Happy Hungry Bunch now. Touched by his words, Yona asks him what he plans to do about his fiancee if he's staying. His frustration snaps and he angrily confesses that he loves her, leaving Yona blushing and stunned, but seemingly finally aware of his feelings. The next day after his confession he acted like it didn't happen and later told Yona that it was okay if she didn't love him back.
Also, Hak is very supportive of Yona and will stand by her side no matter what they face in the future, he will always be there. Finally, in chapter 175, Hak and Yona finally share a kiss after he had rescued her from the Kai castle and was greatly shocked when Yona finally told him that she was in love with him as well.
In the past, Soo-Won and Hak were childhood friends and their bond seemed unbreakable. They both respected and greatly admired the other’s abilities. Due to this, Hak trained vigorously so that he could become someone worthy of being a goal for Soo-Won, who aspired to be as strong as Hak, one day wanting them to walk on equal ground. Hak trusted Soo-Won completely, believing that he could leave Yona in his care, and buried his feelings for the princess. He even offered to be his ‘right hand’ on the condition that he and Yona one day married, promising that he would support them until his dying breath. The two were also mentioned to have raised a falcon named Gulfan together. However, their friendship ended the night Soo-Won murdered the King.
Like Yona, Soo-Won's betrayal hurt him worse than any wound of the body, but initially, he didn't outwardly show it to anyone. Deep inside, he seethes with blood lust and wants Soo-Won to pay for what he did to Yona and Emperor Il, believing it to be his job to one day kill him. When Hak saves the princess from a nest of snakes after she'd gone to look for the hairpin, he gives it to her (having found it earlier), stating that he would never forgive Soo-Won. Because it was given to Yona the night the King was killed, Hak dislikes the hairpin, personally wanting nothing more but to smash it. He believes Yona to still be in love with Soo-Won because she clings to the hairpin. In Awa when he finds Yona crying on the ground after having had an encounter with Soo-Won, he reprimands himself thinking he had become too complacent for not focusing on what he believed to be the real danger and letting his guard down. Thinking of this, he glares off into the distance, causing Jae-Ha to comment on his "sorrowful blood lust."
In chapter 91, Hak succumbs to murderous rage when he finally comes face to face with Soo-Won at the end of the water tribe arc, attacking anyone who got in the way in his warpath to reach Soo-Won, even the other dragons. As Jae-Ha and Kija hold him back, Soo-Won and his entourage make their hasty departure, Hak struggling against the two in his desperate need for revenge. He regains his senses when Yona touches his hand and tells him she's okay, freezing Hak in place when he realizes the extent of his actions. Although Hak despises Soo-Won, it's shown that this stems from how much he cared for his former friend and how he could not fathom that on the day he plotted to kill King Il he gave Yona that hairpin. He stated that on that night when he saw Soo-Won ready to silence the princess, he was struck with so much grief that he "felt his heart shatter to pieces." However, after the incident where he loss control over his emotions after he had seen Soo-Won after the betrayal he later realized that he needed to keep his anger in check and must left go of the past like Yona did.
At first, Hak thinks of Emperor Il as a 'bubbly' king who is a coward. In episode 3 when Hak and Mundok were fighting, Hak called Emperor ll "his Royal Chubbiness". However, when the emperor stopped Tae-Jun from initiating a fight by grabbing the blade of his sword, Hak started to respect him and vowed immense loyalty to him and his family. Because Emperor Il was his master, he is guilt-stricken for being unable to save him from Soo-Won, even saying that he will regret it for the rest of his life. Throughout the dangers he and Yona face, he always asks Emperor Il for his guidance, as well as for the emperor to not take Yona away from him.
Hak regards Yoon as a very valuable person on their team. As Yoon provides them with great meals, he rarely gives out insults towards him like he usually does with Yona and the others. Despite the fact that Yoon is lacking in physical strength, Hak sees him as a very strong person and is able to trust him with looking out for Yona. Like the rest of the Happy Hungry Bunch, he's taken to calling Yoon "mother", in joking reference to his vast talent with household skills. Also Hak is protective over Yoon since he can't defend himself in battle and never teases him like he does with Kija, Jae-Ha and even Yona. In addition to Yoon also knows that Hak is in love with Yona and is trying in his own way to make it clear to her about his feelings, but it is always lost in her denseness. Later in chapter he along with Jae-Ha and Kija were shocked to find out the truth about Yona's previous affection for Soo-Won and the main reason why Hak never told her his true feelings.
Hak forms a rivalry with Kija after the latter asks him to leave Yona’s side stating he was no longer needed. His contempt towards Kija even becomes more complicated when Yona asks Kija to protect him. From then on, he calls him “White Snake” and constantly takes advantage of his entomophobia (fear of bugs). Even with their rocky relationship, Hak considers Kija’s power to be exhilarating as there was no one who fought like him at the castle. They are able to fight alongside each other perfectly despite not initially getting along, as they share the common goal of protecting Yona.
Later, their rivalry seems to have mostly faded and they seem to regard each other as friends, though they still good-nature bicker from time to time. Kija seems to consider Hak an honorary brother, as he asks Hak to call him "Big Brother"–an offer that Hak promptly refuses, though the exchange still prompts an inner monologue about how grateful Hak is for Kija and the others to have them in his and Yona's life.
Their friendship grew greatly to the point where Kija will openly defend Hak and is protective over him as well. For example, Kija, along with Jae-Ha, had to held Hak back from attacking and probably killing Soo-Won in chapter 91 and later in chapter 122 he and Jae-Ha openly defended him when he was threatened by the Sky General Han Joo-Doh when he made it known that Hak should pay for what he did when trying to kill Soo-Won. Also, as the story goes on Kija quite supportive of Yona and Hak's blooming romance, despite his own romantic feelings toward Yona and has made it known that he won't come in between them. This decision is probably due to the fact that in chapter 125 he, Jae-Ha and Yoon had found out about Yona's previous affection for Soo-Won, which is why Hak never pursued any romantic relationship with her.
Though they don't share many interactions, Hak considers Shin-Ah a capable person. He also thinks that as long as Shin-Ah wears his mask, no one can approach Yona easily. When in need of alternative clothing to hide his identity, Hak takes Shin-Ah’s fur and puts it over his head. Hak has never given Shin-Ah a nickname, due to Shin-ah's more gentle social presence and anxiety. Later, they develop quite close, often being shown having casual chats together. Their friendship began more stronger is when Shin-Ah is easily able to tell that Hak is upset following a misunderstanding between him and Yona.
Much like his relationship with Kija, Hak bullies Jae-Ha at every possible moment and smacks him when he flirts with Yona who in turn doesn't know or understand that he's teasing her. During their first encounters, Hak found him to be very talkative and piqued his interest due to his fixation on freedom. Hak also quickly deemed him a pervert, when Jae-Ha's attempts to get him to join Gi-Gan's pirate crew were understandably mistaken for come-ons. When Jae-Ha is revealed to be the Ryokuryuu, Hak become begrudging allies with him, and Jae-Ha immediately takes to teasing Hak relentlessly about his clear affections for Yona. Regardless of initial distaste, he considers Jae-Ha to be a good fighter and even admits that it is inconvenient if he’s not around whenever there is a battle. Hak feels at ease sharing his responsibilities with him. Hak is the only person Jae-Ha does not use the "-kun" honorific for within the Happy Hungry Bunch, suggesting that he considers Hak his equal in maturity. But from time to time he would often tease him for fun in which Hak would hit him in which Jae-Ha loves due him being masochist.
Later, their relationship grows quite close to the point where they would have drinks together and even though they still bicker playfully, Hak seems to use Jae-Ha's "Droopy Eyes" name, less like an insult, and more like a nickname. Also, Hak now sees Jae-Ha as an older brother figure though he will never admit it and Jae-Ha came to replace Soo-Won as Hak's closest friend. Like Kija, Jae-Ha will stand up for Hak and is protective over him as well. For example, he, along with Kija, had to held Hak back from attacking and probably might have killed Soo-Won in chapter 91 because it would put Hak in danger of being executed and he knew at the time that Hak wasn't in the right mental state of mind and later in chapter 122 he and Kija openly defended him when he was threatened by the Sky General Joo-Doh when he made it known that he hasn't forgotten about what had happened with Soo-Won. Likewise, Hak is protective of him as well, this is shown multiple times over the course of the series. For example, when the dragons and Yoon where held as hostages in the Xing Kingdom by princess Kouren he was willing to break them out if they didn't find a peaceful solution to stop the upcoming war between the two countries and again when Kye-Sook openly attacked Jae-Ha and Zeno.
Additionally, Jae-Ha stopped teasing Hak so much about his feelings for Yona as well, ever since learning about Yona's previous affection for Soo-Won in chapter 125 and how hard the betrayal struck him. Also, in chapter 147 Hak asked Jae-ha (In his head) what he can do to get rid of his own hatred for those who would do him and his friends and find forgiveness. The reason why he feels this way was because he realized that Jae-Ha is able to let go of his own hatred and resentment without it cloud his judgment in tough situations and moving foward. This aspect of Jae-Ha's personality and the fact he can remain calm in tough situations made Hak come admire him for it and later feel comfortable enough open up about his inner feelings as shown in chapter 153. When Hak confides in Jae-Ha about his feelings for Yona, explaining that he'd never planned to tell her about them. Jae-Ha congratulates him for the confession regardless and asks off-handedly asks what it was that he had wanted to talk to Yona about while they escaped from Gobi's men back in Xing. Hak falls silent briefly but eventually says that he had wanted to ask Yona if she was truly alright to relinquish her hairpin. He goes on to admit that it may only be him who is stuck in the past, while both Yona and Soo-Won have already moved on.
Out of all the dragon warriors, Zeno is the one Hak understands the least. At first, he doubted that he was the Ouryuu as he appeared frail (despite the said ability of the dragon to be sturdy) and punched Zeno in the face to test if he was the real one. When he had a nightmare where Yona is killed by Soo-Won, Zeno advises him that he shouldn't worry otherwise his life will lessen and nobody would be able to replace him if he dies. Hak thinks the same applies for the dragons warriors, which Zeno appreciates hearing. Zeno notes in chapter 123.5 that, much like the rest of the Happy Hungry Bunch, he regards Hak as rather cute.
- Akatsuki no Yona Chapter 25, Pages 22-23
- Akatsuki no Yona Chapter 05, Pages 23-24
- Akatsuki no Yona Chapter 34, Pages 16-17
- Akatsuki no Yona Chapter 34, Page 21
- Akatsuki no Yona Chapter 47, Pages 25-28
- Akatsuki no Yona Chapter 62
- Akatsuki no Yona Chapter 02, Page 31
- Akatsuki no Yona Chapter 75, Page 25
- Akatsuki no Yona Chapter 11, Page 9
- Akatsuki no Yona Chapter 03, Page 6
- Akatsuki no Yona Chapter 26, Page 14
- Akatsuki no Yona Chapter 23, Page 18
- Akatsuki no Yona Chapter 43, Page 5
- Akatsuki no Yona Chapter 34, Page 25
- Akatsuki no Yona Chapter 17, Pages 14-15
- Akatsuki no Yona Chapter 17, Page 19
- Akatsuki no Yona Chapter 17, Page 20
- Akatsuki no Yona Chapter 18, Page 26
- Akatsuki no Yona Chapter 26, Page 27
- Akatsuki no Yona Chapter 48, Page 25
- Akatsuki no Yona Chapter 27, Page 24
- Akatsuki no Yona Chapter 32, Pages 29-33
- Akatsuki no Yona Chapter 47, Pages 24-27
- Akatsuki no Yona Chapter 55, Page 11
- Akatsuki no Yona Chapter 62, Page 27
- Akatsuki no Yona Chapter 42, Page 22
- Akatsuki no Yona Chapter 62, Page 26