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Sung Il-Hwan (성일환) was a Korean S-Rank Hunter and Jin-Woo's father.
Il-Hwan was a stocky middle-aged man with black eyes, shaggy black hair, and slight facial hair. During his time on the run, he wore a tattered gray cloak over a ragged white undershirt, baggy black pants, and a pair of black boots. When using his abilities, his eyes glowed bright yellow.
Before he went missing, Il-Hwan looked to be around his son's age, with shorter hair and a much cleaner look. He was also pictured wearing a brown jacket over a simple black shirt.
Il-Hwan cared deeply for his family and had little tolerance for those who tried to mess with him or get in his way, as shown when he beat Hwang Dong-Su to a bloody pulp for both lying to him over Jin-Woo's status and lying to the Americans that he was a magic beast.
Around ten years prior to the start of the story, Il-Hwan mysteriously disappeared inside a dungeon during a raid, leaving his family to presume him dead and his wife to raise their children on her own. Six years later, his wife fell victim to Eternal Slumber, leading their son Jin-Woo to follow in Il-Hwan's footsteps and become a hunter in order to provide for himself and his sister, as well as pay for his mother's medical bills.
Around ten years after his disappearance, Il-Hwan suddenly resurfaced in a dungeon on American soil, where he was confronted by a group of American A-Rank hunters. Believing him to be a monster, the hunters attempted to kill Il-Hwan, but he swatted aside their attacks and knocked them out. The FBH then arrested him, but due to Il-Hwan's strength, his lacking knowledge of English, and the fact that a human had never emerged from a dungeon before, they suspected him of being a magic beast with the memories of a human and brought in Hwang Dong-Su to figure out for sure.
Unfortunately, due to Hwang's ego and antagonistic behavior, the interrogation ultimately went south, with Il-Hwan easily defeating him in a fight and bringing down the FBH's building in a sea of flames. Realizing that he was better off on his own, Il-Hwan warned Hwang never to set foot in Korea again, unless he wanted to live a tormented afterlife, and disappeared.
After luring the Frost Monarch to America by deliberately leaving behind mana traces, Il-Hwan attempted to fight and kill him, only to be forced back by the Monarch's superior strength. Their clash resulted in a massive explosion of energy and although it's not made clear if they continued fighting, Il-Hwan later escaped alive.
On the first day of Shinjuku dungeon break, Il-Hwan watched emotionlessly from the top of a nearby building as the gate began to swell and mused to himself that everything was going according to plan.
In their investigation of Christopher Reed's murder, the FBH discovered mana traces within the ruins of his house that were very similar to Il-Hwan's. As a result, they came to consider him as the primary suspect in Chris' murder and issued a red notice for Il-Hwan during the International Guild Conference, exposing the truth to Jin-Woo that his father was still alive.
As the vessel of a Ruler, Il-Hwan was one of the strongest hunters in the world, as demonstrated by how he was able to beat Hwang Dong-Su so bad that the latter was forced to spend several months recovering from their fight in the hospital. Compared to the other vessels, however, Il-Hwan knew about the origins of his powers and was thus much more knowledgeable in using them. He was even able to use a skill that granted him his Ruler's full power and boosted his strength so much that he was able to hold his own against both the Frost Monarch and the Beast Monarch at the same time. Unfortunately, as his body was unable to withstand so much excess power, this skill came at the cost of his own life.
- Stealth: Just like his son can, Il-Hwan was able to camouflage himself with his surroundings, essentially turning himself invisible.
- Ruler's Hands: Il-Hwan was able to control and move objects via telekinesis.
- Spiritual Body Manifestation
- "Don't you ever set foot in Korea. I'm not saying this for my son's sake, I'm saying it for yours. You will never rest in peace, even in death."