Seo Yuna (Kor. 서윤아) is an ordinary human and a support character of the series. She is a student of Ye Ran High School and a close friend of the Frankenstein household, where she regularly hangs out with the rest of the gang.
Yuna is a pretty young girl with brown eyes and long, straight hair which she lets fall over her shoulders. Her hair color appeared dark brown in former illustrations but changed to black in later volumes. She is usually seen wearing a round collared T-Shirt when not in the school uniform.
Yuna is a timid, quiet and benevolent girl who is also often shown to be quite naive. She is very soft spoken.
Seo Yuna (Kor. 서윤아) is Shinwoo's and Ik-Han's childhood friend. It is later shown that she is also a childhood friend of Suyi. Yuna is a student of Ye Ran High School and is in the same class as Shinwoo, Ikhan and Rai. Shinwoo had a crush on her since they were kids. However, after he was rejected by Yuna, he decided to move on, while still remaining as a close friend of Yuna. Yuna, on the other hand, is shown to have a huge crush on M-21.
One day, while returning home after school, Yuna sees a man slumped in an alley. She gets worried and goes to him while asking whether he was alright. However, this man is an infected person in search of food, and Yuna gets assaulted by him. Luckily, Shinwoo, Rai and Ikhan who were walking nearby, heard her screams and came to her rescue. Later Yuna is kidnapped by M-21 and M-24 to lure out Shinwoo to fight the Infected for their entertainment. After M-21 calls Shinwoo using Yuna's phone, Shinwoo and Ik-han arrive to rescue her.
M-21 tells Shinwoo to fight the Infected if he wants to free Yuna. And if he doesn't do as he says, M-21 threatens to kill them all. Due to these conditions, Shinwoo has no choice but to fight. At first, Shinwoo was only slightly suspicious of the Infected not being normal. However, as he fought, Shinwoo noticed that none of his normally lethal attacks have any effect on him. His opponent just continued fighting as though he couldn't feel the pain. M-21 and M-24 are quite shocked after seeing how strong Shinwoo was. But, naturally, being an ordinary human fighting an Infected, Shinwoo started losing, causing Ikhan and Yuna to worry.
Meanwhile, Rai and Frankenstein are on the way to find the kids. Upon arrival, Frankenstein releases his dark aura to catch the attention of M-21 and M-24. M-21 and M-24 went to meet them, thinking that they were weak. This provided Ikhan with the opportunity to move Yuna away from the fight. However, they are proven wrong when M-21 is instantly defeated by Frankenstein and M-24 is defeated by Rai. Rai and Frankenstein spares their lives. The children are saved upon the arrival of Rai and Frankenstein, although Shinwoo had gone through a lot of beatings and Yuna had trouble walking.
Once, Yuna and Shinwoo are on their way to Frankenstein's house when they see a foreigner being robbed by some local delinquents. The foreigner, Takeo, is saved by Shinwoo. When he sees Yuna, Takeo confuses them for a couple on the date, embarrassing them. Yuna and Shinwoo join Takeo at the cafe and get acquainted. However, they are spotted by Shark who targets them as witnesses marked for annihilation.
Yuna and the gang are kidnapped by Shark and Hammer. They are taken to the DA-5's hideout and are held as hostages, in order to capture Regis. Shark also intended to use the kids to threaten M-21 as he knew them. However, Shark also states that the children can be killed now, as Takeo and Tao had contact with them. Shark states that the girls in Korea are very pretty. And when Yuna gained consciousness and asked Shark why he kidnapped them, he replies by saying that their voice is nice. Shinwoo then asks Shark why he had brought them there, Shark responds by kicking him and standing with a foot on Shinwoo's head. Regis wakes up to the sound of the kids screaming.
Now that everyone is awake, Shark calls M-21, causing the kids to notice him. M-21 doesn't want the DA-5 to know that he knows the kids. So, he tells them that he doesn't know the kids. This causes Yuna and the others to be visibly shocked. Shark gets angry but grins like a maniac, saying that if so, there is no use of keeping the kids alive. M-21 is distressed. He wants to find out the names of his comrades, but he also doesn't want any of the kids to get hurt. In the end, without even thinking, M-21 asks Shark to let the kids go. They are later saved by Rai.
|Rai's Group||Rai · Frankenstein · M-21 · Tao · Takeo · Shinwoo · Ik-Han · Yuna · Suyi|
|Nobles||Raskreia · The Previous Lord · Gejutel · Karias · Krasis · Kei · Lagus· Claudia· Gradeus· Edian · Ludis · Ragar · Rajak · Rozaria · Seira · Rael · Regis|
|Werewolves||Muzaka · Maduke · Lunark · Kentas · Ashlyn · Garda · Grui · Gaitan· Kuharu · Mount · Drakon · Kaiyo · Juraki · Gayare · Mirai · Urne · Uzhir · Gorma · Krano · Dorant · Braang · Zaiga · Gaura|
|Union Elders||1st Elder · 3rd Elder · Roctis ·Lunark · Urokai · Zarga · 8th Elder · 9th Elder · Rostere · Muar · 12th Elder · Dr. Crombel|
|Union Agents & Members||Dr. Aris · Bonerre · Hammer · Ignes · Infected · Jake · Kalvin · Ked · Krantz · Lutai · Mark · Mary · Rodin · Shark · Taze · Yuizi · Yuri|
|KSA||Lim Taesik · Sangeen · Yonsu|