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. The harsh words he gave to 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.
It's been noted that Yoon sleeps with Yona in the same tent while the Hak and the dragons sleep outside as seen the few times when Yoon asks Hak to sleep with Yona if a bear or another creature or person 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. From this- and other factors- Yoon and Yona built a sort of familial relationship, almost like siblings or parent-child. Yoon comes to criticize Yona's reckless behavior and is often the one to try to stop Yona or first hug Yona after doing something reckless- usually teary-eyed (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 friend. They are seen constantly talking to one another and joking around. 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"
And when Yoon nearly dies in the Awa Arc in order to protect Yona and Yuri despite having the fireworks he reveals his identity knowing full well he may die.  As time went he began to harbor a close, sibling-like relationship with Yona and is there for her emotionally.
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. Likewise, Hak relies on Yoon for great meals or else he won’t eat. Yoon is rarely teased by Hak compared to others. Despite Yoon being anxious and lacking in physical strength, he still promises to Hak that he will protect Yona no matter what happens.
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 see Kija’s affection towards the princess.
Whenever someone needs to guard the fort, Shin-Ah is someone Yoon considers to take the position due to how his mask attracts attention. Even with that gag, Yoon knows that making Shin-Ah take off his mask will probably take a long time because his fear will take a long time to get rid of as it is something permanently embedded in Shin-Ah’s mind. That is why whenever a stranger tries to take off Shin-Ah’s mask, he tries to stop them to not make Shin-Ah get nervous.
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. During the Xing arc, Yoon had saved Jae-ha from death when Yotaka was about to kill him by standing in the wa, and similarly kept the Xing troups from taking 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.
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 rest of them getting suspicious. He also claims Yoon to be a rather scary boy and later starts to respect him. 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.
- 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 36, Pages 22-28
- 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