Na Yonsu (Kor. 나연수) is a modified human and an agent of the KSA. She is married to An Sangeen, a fellow KSA agent and her current work partner.


She has turquoise eyes with short dark hair except for long bangs and a small, knee length ponytail. She dons a black pantsuit with white blouse. She is always seen with her husband An Sangeen.


She is a hotheaded person, prone to anger with passion for her country, leading her to investigate the big explosion (caused by Frankenstein and Rael Kertia ) despite strict orders from her higher ups. Yonsu has a deep love for her country and her comrades as she was seen crying after the Cerberus attacked the KSA and many members were killed.


Na Yonsu is an experiment conducted in Korea without the Union headquarters acknowledgement, so her abilities are kept a secret. She is married to An Sangeen.

Plot Overview

Volume 4


Na Yonsu first appears with her partner while investigating the big crater (created from the collision of Frankenstein and Rael) in the city. However, their higher-ups assign her and Sangeen with another mission - assessing the suitable candidates for KSA's future agents. So, they have to temporarily abandon investigating the crater.
For the given mission, Yonsu and Sangeen visit Ye Ran but Yonsu gets into a squabble with M-21 while attempting to enter. Later, she and her partner return with permission to see the Chairman and with superior back-up, they manage to infiltrate the school. Yonsu joins as the temporary P.E. teacher at Ye Ran High School. During that time they place the children in danger to test the skills of Shinwoo and Ikhan as possible recruit candidates. But due to the special security's observation, she and her comrade couldn't accomplish their task. Furthermore the issue, when brought to the Chairman's notice, gets them dismissed from the school.

Cerberus Arc

A short confrontation with M-21 leads Na Yonsu to grow suspicions regarding M-21. So, despite the reluctance of Sangeen, embarks on a vigil in Ye Ran grounds at night to find out M-21's identity. There she battles M-21 and after a short clash, both of their enhancements are revealed to each other. When they confirm none belongs to the Union, they decide to end their duel. The KSA agents discover the identities of the trio who reveal that they are aware of their identities and secrecy as well. They settle with a co-operative deal.
Later, Yonsu and Sangeen are given the mission to aid Cerberus in their investigation, to which they engage reluctantly. She gets worked up and reveals Sangeen is her husband when Cerberus members hurt him (an act planned by Sangeen to meet the guard trio). Later, Ked and Lutai discover the identity of An Sangeen as a modified human. Na Yonsu comes to know about this and she goes to help An Sangeen and the RK.

The 12th Elder Arc

Yonsu meets Sangeen on her way to the battle location. They decide to help out the trio and arriving the scene, they find M-21 already struggling against Ked. Yonsu joins to help out shortly but proves no match. Later, both she and her husband watch from the sidelines as the Cerberus and the 12th Elder get annihilated. There they learn about the identities of Rai and Frankenstein as powerful beings.

Volume 5

The KSA agents maintain complete collaboration with the trio, informing them every news they get from the Union. On one evening, they notice a chaos in the city alleys and inform the trio. But before either group arrive at the spot, Rai, Regis and Seira find a fleeing experiment desperately fighting his pursuers. When the KSA agents arrive, Regis has already taken care of the pursuers and the agents take the experiment to their treatment faculty as Rai seems to know the modified human. Later the trio arrives there to find that the modified human is M-24.
In the following arcs, Na Yonsu and An Sangeen are rarely shown.

Volume 8

Na Yonsu is present when Lunark visits the KSA Headquarters looking for Frankenstein.


On the process of writing the summary

On the process of writing the summary

On the process of writing the summary

On the process of writing the summary

Powers & Abilities

Yonsu kick

Energy imbued kick

She is a modified human and shows characteristic strength. Even with the minimal application of her power, her attack left slight signs of impact on M-21's palm. Though she couldn't injure M-21 but she was able to fight on par with him for sometime.

Aura Manipulation

Unlike Sangeen, who materializes his energy, Yonsu imbues her aura in her limbs to enhance her attacks.



Rai's Group Rai · Frankenstein · M-21 · Tao · Takeo · Shinwoo · Ik-Han · Yuna · Suyi
Nobles Raskreia · The Previous Lord · Gejutel · Karias · Krasis · Kei · Ludis · Rael · Ragar · Rajak · Regis · Rozaria · Seira · Claudia · Edian · Gradeus · Ignes · Lagus · Roctis · Urokai · Zarga
Werewolves Muzaka · Maduke · Lunark · Kentas · Ashlyn · Garda · Dorant · Juraki · Grui · Gaitan· Kuharu · Mount · Drakon · Kaiyo · Gayare · Mirai · Urne · Uzhir · Gorma · Krano · Braang · Zaiga · Gaura · Gotaru · Bashum
Union Elders 1st Elder · Maduke · 3rd Elder · Roctis ·Lunark · Urokai · Zarga · 8th Elder · 9th Elder · Rostere · Muar · 12th Elder · Dr. Crombel
Union Agents & Members Dr. Aris · Bonerre · Geo · Hammer · Haydn · Ignes · Infected · Jake · Kalvin · Ked · Krantz · Lutai · Mark · Mary · Rodin · Shark · Taze · Yuizi · Yuri
KSA Lim Taesik · Sangeen · Yonsu
Others M-24