This article contains details from the manga that are not covered in the anime. Proceed with caution.
Min-Soo has orange brown hair and a pair of green eyes. He is mostly seen wearing his attendant uniform; it consists of a brown tunic held by a purple sash over a pale green robe, white long wristbands tied in a black ribbon with a crisscross pattern on top of his tunic's sleeves, dark olive pants and black boots. He also wears a long white bandanna around his forehead.
Min-Soo is a very caring person who was attentive to the needs of Yona and Emperor Il. He had a close relationship with the royal family and Hak. Min-Soo wasn't just a mere servant but also a confidante to the people he served for as he was seen present in some important discussions. Because of his loyalty to the royal family and his duties, he is also selfless, as seen when he willingly sacrificed himself for Yona and Hak's safety.
Min-Soo assists Princess Yona to her room before attending Emperor Il’s speech in the courtyard. He tells her that she should get there soon, but the princess doesn't listen to him. Emperor Il and later, Hak, enters the room and he watches the three of them talk animatedly with each other. The following day, Min-Soo is cleaning Soo-Won’s room when Yona arrives. He tells her that Soo-Won is with Hak on the training grounds. Soon after, he witnesses the argument between Yona and her father about her future marriage and Emperor Il’s refusal to accept Soo-Won as the princess’s husband.
Days after, Yona’s 16th birthday arrives and Min-Soo carries his duty at the banquet. When Min-Soo sees Emperor Il frustrated at how Yona acted towards him due to their fight, he offers the elder a drink to calm him down. Later that day, Min-Soo checks on Hak and brings him a drink. Soon, Min-Soo sees the fight between Hak and Yona against Soo-Won and a handful of soldiers. He shoots an arrow to distract the enemies so that Hak and Yona could escape.
They meet behind a building and Min-Soo asks if Emperor Il truly died. After confirming the happenings and seeing how broken the princess is, he offers himself as a decoy so that Hak can get Yona away from their pursuers. As they carry out their plan, Min-Soo tells the princess to be safe before running to the opposite direction while covering himself with a robe. He successfully gains the guards’ attention, allowing Hak and Yona to gain access of the gate. However, Min-Soo is thought to be dead after being shot by the archers in the process.
One day, Min-Soo and Lili collide in Hiryuu Castle. After exchanging apologies and walking away from Lili, she notes that his movements are a little stiff. Lili's observation implies that when Min-Soo was shot in the leg on the night of Hak and Yona's escape, he is unable to walk the same way.
Although Yona intended to meet with Soo-won to discuss issues regarding Kouka and Xing, it is Min-Soo who appears in the emperor's place. Yona thanks him for saving her and Hak on that first night but he refuses her gratitude and tells them that he is a servant of Soo-won. Min-soo hands Mr. Ogi a letter saying that Soo-won will not negotiate things peaceably. Min-soo explains that Soo-Won is fully aware of the hatred of Princess Kouren. While aware of the fact that a peaceful negotiation could happen, Soo-Won believes this will be only temporary. Min-Soo informs Yona that Soo-Won already started to mobilize his army in preparation for the war against the Xing Kingdom. Yona and Hak don't understand why Min-Soo became a servant of Soo-Won and question his loyalty toward the Emperor II. Min-soo informs them that this isn't true. Min-soo begins to tell her what happened. When he was young, his mother was a medical worker under Soo-Won's mother, Lady Yong-Hi. As a result of this, he grew up in Soo-Won's mansion and was acquainted with Soo-Won. When Min-soo was fourteen, he passed his trials to become a medical officer and became a servant for King Il. From his time at the mansion, he became acquainted with Kye-Sook. In their conversations, he gave Kye-sook information about the state of the palace. However, since Min-soo was unaware of the planned treachery and assassination against King II, he unknowingly gave up valuable information to Kye-Sook.
Due to these events, Min-soo says that he doomed King Il to die and asks Yona to kill him. Yona instead forgives him. Yona informs him that he atoned for his sins by helping her and Hak escape from the castle that night. The fact that she and Hak are still alive was because of Min-soo's sacrifice. Since Yona knows that Min-Soo was deeply loyal to her father and was completely unaware of Soo-Won's plan, she is satisfied that what Min-soo thought about her father wasn't a lie. Yona tells him that she won't live a life that is fueled by hatred. Instead, Yona tells Min-soo that she just wants to stop this war and prevent unnecessary bloodshed. Yona tells Min-soo her personal reason for wanting to stop the war. Min-soo then informs Yona and Hak that Soo-Won is planning to use the Wind Tribe and Sky Tribe in the war against the Xing Kingdom. As Min-soo takes his leave, Yona tells him that regardless of his reason for coming here, she thanks him for coming. Touched by Yona's words of gratitude, Min-soo begins to cry. Surprised by Yona's change, Min-soo wished in his heart that he could talk to Emperor II one more time.
Min-soo eventually returns to the castle and Soo-Won compliments him for his work. Min-soo informs Soo-Won that both Yona and Hak wish for a peaceful negotiation as well as their personal reason for wanting to stop the war. Min-soo asked Soo-Won if the war between the two kingdoms is unavoidable. After a moment of silence, Soo-Won informed Min-soo that if he doesn't choose the right path that he believes is best for the kingdom, there was no reason for him to ascend to the throne. Min-soo asks Soo-Won if it is for that reason that he is willing to inflict more suffering upon that person (Yona). Soo-Won sadly informs Min-soo that any country ruled by a ruler who prioritizes one person over his/her country would fall to ruins. Min-soo remembers that Kye-Sook told him that the only reason that he is spared from death is because of Soo-Won's consideration toward Min-soo's mother. While Min-soo holds resentment toward Soo-Won and can never forgive him, he knows that Soo-Won wouldn't be able to move his country forward if he embraces kindness.