Ik-Soo becomes the father-figure for Yoon. However, Yoon is more of a guardian instead of Ik-Soo as the latter is incapable to manage his self carefully, often tripping on a flat ground much to his annoyance. Because of this, he mastered how to make medicine and to cook food for the sake of Ik-Soo. Despite the unreliability and idiocy of Ik-Soo, Yoon knows that he is someone who doesn’t lie and grieves over the fact that he can’t help people in need. Moreover, Ik-Soo’s words are absolute for him.
When he was young, Yoon abandoned his goals of travelling just to be with Ik-Soo as he believes that the priest will be helpless without him. However, Ik-Soo still wants him to achieve his dream, and upon Yona’s arrival, the priest takes this opportunity to make Yoon's desire come true. They have a small fight due to this but later reconcile with each other and at that time, Ik-Soo, despite his decision to send Yoon away, confesses that he will be lonely without the young boy anymore.
Yona and Yoon's relationship starts off as a little shaky due to Yoon's hatred for royalty. Yoon criticizes Yona for her ignorance and selfishness and points out that she hasn’t thanked him for taking care of her or even the possibility that she hasn’t thanked Hak who always looks out for her. Despite their small quarrel due to Yona's naive nature, Yoon still takes care of her even if she is a person of royalty. Also, he realizes that he is just as naïve as her as he only knows what he knows.
As they take on their journey, the bond between them becomes better and they become friends over time. Yoon is able to be relaxed and laugh together with her. Even when he can’t fight, Yoon still protects Yona and makes himself as a shield before anyone can hurt her. During the Awa Arc, Yoon tries to distract Lord Kumji from Yona despite risking death. The harsh words he used with Yona on their first meeting still weigh on his mind even though Yona doesn’t mind it anymore and by that, he apologizes to her which Yona finds adorable. When Shin-Ah calls Yona by her name, he asks if he can call her in her name too as he finds “Princess” too long to say, and Yona agrees to it. The two of them promised to each other that they will grow strong for the sake of Kouka’s people; Yoon often feels guilty that he is physically weak and incapable of protecting his friends as they do him.
It's been noted that Yoon sleeps with Yona in the same tent while the Hak and the Dragons sleep outside, as seen when Yoon asks Hak to sleep with Yona in case a bear from the wild area were to attack. The Dragons, Hak, and Yona are unbothered that he sleeps in the same tent as Yona since they usually forget that he is a boy. Partially due to him not being viewed by Yona as a male romantic prospect, Yoon and Yona build a familial/sibling like relationship. While Yoon is sometimes seen to be overly concious of or flustered by Yona (i.e. blushing while treating her back wound in the Water Tribe), any possible crush from his side is seen to dissipate although he cares for her deeply. Yoon comes to criticize Yona's reckless behavior and often tries dissuading her, tearily hugging Yona after doing something reckless (I.E the Awa Arc. when she walks across the cliff). Yoon feels helpless that he doesn't have the power of the dragons, or strength like Hak's to help or protect Yona and hopes the least he can do is protect Yona's smile. Yoon is, besides Hak, Yona's closest friends and is a companion to her. They are seen constantly talking to one another and joking around. Yoon is aware of the mutual feelings between Hak and Yona and is supportive of them, although he tires of their mutual obliviousness and resolves to stay out of their business. They both drive to protect and help the other and often worried about the other; Such as when Yona follows Yoon after sneaking out saying "You left so stealthily I got worried" and offers to help the Fire Tribe as it's Yoon's home and to see the effects of her father's doings.
Yona: "You're helping out this village right? We'll help you!"
Yoon: "You can't! You'll attract attention!"
Yona: "We'll try our best not to!"
Yoon: "That's impossible! You attract attention just by being alive! This place has sick people and isn't safe, this isn't the kind of place a princess should come to."
Yona: "-Yoon. It is because I am Kouka's princess and especially because I am King Il's daughter, that I think it is a place I should come to. I want to know the effects of the things my father did"
The first time Yoon sees Hak, he already perceives that the latter has feelings for the princess but doesn’t dwell too much on it like Jae-Ha. Yoon trusts in Hak for military knowledge and his strength to avoid trouble when they travel - Yoon generally refers to him as his nickname, Lightning Beast. Hak relies on Yoon for meals and medical care, and is relieved that Yona has found other trusted companions. Yoon is rarely teased by Hak compared to others and they both rely on each other. Despite Yoon being anxious and lacking in physical strength, he still promises to Hak that he will protect Yona no matter what happens and Hak has faith in him. Much like how Hak treats Yona, Hak trusts Yoon but is still protective of him. When the Dragons, Yona, Hak, and Yoon resolve to go to Hiryuu Castle, Yoon stays behind the gates when Hak is prevented from entering and promises to stay with him. The two support each other while separated from the others, Yoon keeping Hak levelheaded.
With Kija being a pampered and sheltered man, Yoon is scared for him when he is leading the way and believes that he should just follow instead of being in front. However, Yoon greatly relies on Kija’s dragon sense to make out the locations of the dragons while he consider the military movement together with Hak. Like how Yoon can see Hak’s feelings, he can also clearly see Kija’s affection towards the princess. Like the rest of the Dragons, Yoon becomes a pseudo mother figure to Kiji (the latter jokingly calling Yoon "Mother" with the rest of the group). The two care about and trust each other.
Whenever someone needs to guard their base, Shin-Ah is picked by Yoon due to how his mask attracts attention. Yoon knows that getting Shin-Ah to take off his mask will probably take a long time because his fear is something permanently embedded in Shin-Ah’s mind. Due to this whenever a stranger tries to take off Shin-Ah’s mask, he tries to stop them to not make Shin-Ah get nervous. Shin-Ah loves Yoon's cooking - when Yona, Kija, and Shin-Ah are all acting strangely after eating mysterious candy, Yoon immediately calms Shin-Ah with the promise of food. When Shin-Ah is possessed by the spirit of a previous Blue Dragon, Yoon is very worried and attempts to free the group from where they are trapped. Yoon cares deeply for Shin-Ah and worries over his health the same way he does with all the Dragons.
In the anime, the two rarely interact, save for when Yoon scolds him. In the manga, Yoon has a good relationship with Jae-ha, and is exempted mainly from the same teasing as the rest of the group (save for an occasional 'mother' gag). Jae-ha has protected Yoon during battle multiple times just as Yoon has repeatedly treated his wounds. During the Xing arc, Yoon had saved Jae-ha from death when Yotaka was about to kill him by standing in the way, and similarly kept the Xing troups from ripping him away again. He also acknowledges that Jae-ha is good to have during a problem, such as when Yona, Kija, and Shin-ah were suffering from the effects of the cough drops. The two are both very aware of the social situations within the group, for example the romance between Hak and Yona. Yoon cries and is comforted by Jae-ha upon discovering the short live spans of the Dragons.
Zeno first joined the group because of Yoon's superb cooking; according to him, he's "attracted by the smell of tasty food". Later this was revealed to be an excuse he used to meet Yona without arousing suspicion. He also claims Yoon to be a rather scary boy and later starts to respect him. Zeno often let himself be mothered by Yoon, and sometimes (after his immortality reveal) played up his 'old age' in an attempt to avoid chores. When speaking of the others not in their presence, Zeno often shows his age by referring to the young Yoon in a sentimental, sage manner. He also shows concern for Yoon and has the habit of calling him "kid" (sometimes also translated as "lad"). Similar to the rest of the Dark Dragon and the Happy Hungry Bunch, the two share a mother-child relationship gag that is more pronounced by the fact that Zeno, personality wise, acts like the youngest of the group while Yoon, with his great knowledge and care for the others, acts like the mom of the group. Yoon cares deeply for Zeno and is upset whenever he's hurt despite regeneration. In terms of character interaction, the two are paired up often
- Akatsuki no Yona Chapter 13, Page 20
- Akatsuki no Yona Chapter 13, Page 23
- Akatsuki no Yona Chapter 12, Page 14
- Akatsuki no Yona Chapter 14, Page 30
- Akatsuki no Yona Chapter 12, Page 11
- Akatsuki no Yona Chapter 14, Page 4
- Akatsuki no Yona Chapter 12, Pages 8-9
- Akatsuki no Yona Chapter 14, Page 29
- Akatsuki no Yona Chapter 25, Page 18
- Akatsuki no Yona Chapter 25, Page 17
- Akatsuki no Yona Chapter 48, Pages 10-11
- Akatsuki no Yona Chapter 43, Page 5
- Akatsuki no Yona Chapter 34, Page 25
- Akatsuki no Yona Chapter 18, Page 7
- Akatsuki no Yona Chapter 26, Page 24
- Akatsuki no Yona Chapter 30, Page 26