|“||But sometimes, because they conceal themselves, they actually appear smaller than they are.||”|
Yu Han Sung (유한성, Yoo Hahnseong; or "Yu Han-Sung") is a High Ranker and the Test Director of the Second Floor. Notably, he is a key member of FUG in taking Viole to the top. He is the main antagonist of Part I.
Appearance and Personality
Yu Han Sung is portrayed as a man with long blonde hair and quite feminine or, rather, androgynous features. He always wears a hanbok, usually blue and yellow.
Yu Han Sung has been seen as an extremely intelligent and perceptive individual. He is addicted to instant food, which is the cause of many jokes directed at him. Behind this simple outer shell, lies the deadly "Submerged Fish" who destroys those who may pose a threat to the Tower.
Also, he probably recognised and admired Koon Aguero Agnis' talents but relished the thought of crushing him as he likely couldn't tolerate the existence of another "genius", due to his own pride and ego.
Despite his abilities that could easily grant him a better job on higher Floors of the Tower, Yu Han Sung remains as the 2nd Floor Test Director to fulfill FUG's goals. He claims that one must "weed out those who will bring harm to The Tower". However, he is recognised for his strength which Lo Po Bia Ren stated "impressed even the Vice Commander".
Yu Han Sung was one of the Rankers proctoring the tests on the Second Floor. He directly proctored the Door Test and observed the groups of Regulars as they attempted to pass it. When Koon's team passed the test, he noticed that Koon was hiding Regulars inside his bag and subtly hinted to Koon that he knew. When all the Regulars had taken the test, Yu Han Sung discussed some of the Regulars' methods of passing with his test assistants.
After Quant informed him that only three Regulars had passed the "Deathmatch" Test and also that an Irregular and Zahard's Princess were in the group, Yu Han Sung was left in a serious predicament. If Evankhell found out, there would be severe repercussions for the both of them. However, Yu Han Sung thought up a plan to deal with the problem: the Crown Game.
Later, Yu Han Sung discussed the results of the Crown Game with Lero-Ro. He stated, that the Floor of Test was to filter dangerous individuals before they could enter the Tower.
Later, Yu Han Sung observed the Hide-and-Seek Test with Lero-Ro. He is in charge of grading the overall team. He talks to Lero-Ro about Koon's performance, cryptically noting that Regulars would have to drop off "excess weight", signifying their comrades, as they climbed higher and higher up the Tower. He also reveals his cruel side, as he states that he wanted to destroy Koon due to his multi-faceted personality.
During the wait until it was time to announce the results, Rak bumped into Yu Han Sung, disrespected him, and was subsequently compressed to a small size.
Before announcing the results of the Position Test, he tracked down Ren and engaged him briefly, before stating that their goals were the same and that there was no reason for them to fight. He revealed his power to Ren as the "Submerged Fish" of the Second Floor.
Following the announcement of the results of the Position Test, Mauchi got angry at the Rankers overseeing the tests. After being called down to discuss why he thought the results were wrong, Yu Han Sung snapped his bones with Shinsoo. Koon then also disagreed with the results and came down and said that he wished to get a test from the Guardian, to which Yu Han Sung replied that he was insane and that to get such a test one would need to be an Irregular. When Baam revealed that he was an Irregular, Yu Han Sung allowed him to see the Guardian. Afterwards, he told Baam that he had been trying to destroy him all along.
During the Submerged Fish Hunt Test, after Evan Edrok and Kurudan burst into his quarters, Yu Han Sung revealed to them that everything had been planned by the Guardian and that the seemingly unusual events were part of the test.
Later on, Yu Han Sung gave the passing Regulars special rings as a graduation gift before they ascended to the next Floor. After they had gone up, Lero-Ro quit his position as a Test Admin causing Yu Han Sung to fire Quant too as he considered them a "Set Menu". He was finally seen communicating with someone else via his Pocket assuring them that the Zahard Family would think Baam was dead.
He was contacted by the 20th Floor director, Augusgus, who referred to him as the "Submerged Fish".
In a flashback set three days after Baam's presumed 'death', it was revealed that the rings given to the Regulars were custom-made with tracking devices. As he handed over Baam's friend list as he stated, "Starting from today we will start your training to become a Slayer. For each and every-time you show a shred of weakness we'll kill one of your friends. You will know how many survived, once you've climbed The Tower... Jyu Viole Grace-nim".
After saving Baam and Androssi Zahard from suddenly being crushed in the quarantine area, a data version of younger Yu Han Sung commented that his long wait had finally "paid off". When Baam and Androssi woke up, he introduced himself as the data of Yu Han Sung as a Regular. When questioned, Han Sung cryptically remarked that he knew the two of them would arrive at the quarantine area. While guiding Baam and Androssi out of the quarantine area, the group was attacked by Baam's nemesis. In the ensuing fight, Han Sung attempted to crush Baam's nemesis to death using a suspended trap however, much to his surprise, Baam saved his nemesis instead. The fight continued, but was quickly interrupted by the appearance of a giant soldier patrolling the quarantine area. Androssi teleported Han Sung and the rest of the group away using Bong Bong. Baam's nemesis was then tranquillised by Batis, a data human that Han Sung allied with.
The group moved into the seed, a shelter within the quarantine area. Here, Han Sung explained that the group had to escape the Fruit of Good and Evil before the heroes outside cleared the stage, or else they would be trapped until another group of heroes arrived. He then explained that the people trapped within the fruit had already died several times trying to escape. The prisoners managed to find an exit, however, they were never able to get through the final door. Han Sung then said that Baam would be able to break through the door. To this, Baam said that they should leave immediately, as his teammates outside would be able to clear the first stage very quickly. Han Sung agreed, however at this moment, Baam's nemesis awakened and the giant soldier attacked the seed. After Baam defeated his nemesis, Han Sung revealed that he had planted bombs throughout the seed. The prisoners escaped the seed and Han Sung detonated the bombs. When Baam showed hesitation due to the 'death' of his nemesis, Han Sung explained that the Big Breeders, responsible for trapping the prisoners within the fruit, were the henchman of young data-Zahard and that they ensured nobody who arrived at the Hidden Floor could find him.
While progressing towards the exit, the fruit was shaken as the Big Breeder arrived to present the grand quest. Batis suggested that he, Han Sung, Baam and Androssi should take the shortcut and escape so that they could stop Big Breeder in time. Han Sung explained that there was a more dangerous path, but if they didn't hurry, everyone in the fruit would die. By making holes through the fruit's tunnels, Han Sung created a shortcut leading through the fruit's shelters and straight to the exit. After finally arriving at the exit, Baam successfully broke open the door. With this, and while looking at Baam, Han Sung mentally noted, "I knew it. This is the guy! V...". Having escaped the fruit, the group begins to move towards Big Breeder. However, the demon holding the fruit awakened and attacked the group. Realising that he needed to attack the main body, Baam asked Han Sung to amplify his shinsoo. Through a combination of Baam's attack and Han Sung's amplification, the demon was annihilated and the group managed to arrive at Big Breeder's location. Han Sung then told Baam to go through the door behind Big Breeder, as the real Big Breeder was hiding behind it.
Powers and Abilities
Yu Han Sung is a powerful High Ranker of FUG and apparently a genius Wave Controller. An example of his strength is his ability to easily summon and control an enormous fish close to the size of a White Steel Eel. It can be considered that he was an incredibly powerful genius when he climbed the Tower. Ren stated that Yu Han Sung possessed power that even shocked RED's Vice Commander. He is the standard of a High Ranker's strength. When Yu Han Sung said he didn't want to fight Ren, it wasn't him being afraid of Ren's power, but rather the political consequences of battling against a RED member.
Shinsoo Manipulation: He is a master of Shinsoo manipulation, mostly known for his position as a Wave Controller. He was also able to sense that Koon had extra Regulars hidden in his bag, after he passed the Door Test.
- Shinsoo Bubble: Yu Han Sung is able to create a Shinsoo Bubble in order transport people or move things. 
Yu Han Sung Style: Yu Han Sung developped his own Shinsoo control style.
- Amplification Skill - Boiling Mass: This is Hansung's special skill. He uses a wave to maximize the effect of Shinsoo. Using this skill it is hard to attack with precision, even though you can significantly amplify even a small amount of power. 
Wonsulsa: It is unknown if he is a legitimate Wonsul user, or whether he learnt Wonsul naturally.
Dansulsa: He is apparently a Dansul user.
- (To Koon Aguero Agnis after the Door Test) "Your bag seems very heavy."
- (About Koon Aguero Agnis) "He's such brilliant boy. That pride, courage, talent, cunningness and arrogance. I just want to break him into pieces."
- (To Lo Po Bia Ren) "This is Evankhell's Hell where we sort out the dangerous from the Tower. And I am the Deep See Fish lying in wait to gobble them up."
- (To Rak Wraithraiser after compressing his form) "Huh? I'm sorry. I couldn't see you because you were too small. Oh my. Sorry. Too small. One moment. Just one more spin..."
- (To Rachel) "I've received word from Headon-nim. Miss Michelle Light. It must've been tiring to complete the first test. Ah, perhaps it wasn't too difficult. Since you were with a person Headon-nim prepared..."
- (To Rachel) "Miss Michelle, you need not worry about anything. The teammates you'll need, the rights, and strength, I will steal all of it for you."
Notes and Trivia
- Rak referred to Yu Han Sung first as "Golden Turtle" and later as "Coffee Addict Turtle".
- He is the endorser of the Maxim coffee brand as seen in a vending machine.
- According to SIU, he is deeply connected to Hendo Lok Bloodmadder.
- SIU stated if Yu Han Sung didn't mess around on Evankhell's Floor, his rank would have been similar to Yuri's.
- It is yet unknown how Han Sung obtained knowledge on V whilst still a D-rank Regular.