Sung Jin-Woo is the main protagonist of Solo Leveling. Originally an infamously weak E-Rank Hunter, he got the chance of a lifetime when he was selected as the Player of the System, giving him the unique ability to grow in strength without restraint.
Jin-Woo is a confident individual with a strong sense of family and a thirst for power. As a result, he is very close to his mom and sister and rarely wastes an opportunity to grow stronger.
Despite being strong and respected, Jin-Woo isn't arrogant and is both polite and easygoing in person. He is also mostly indifferent to materialistic desires such as fame and fortune and can be very selfless. In battle, however, he is ruthless, slaughtering his enemies indiscriminately and even somewhat disdainful.
When he was weak, Jin-Woo was very timid and insecure due to his incompetence as a hunter and his troubled family situation. Although he cared deeply for his family and spent years risking his life going on raids for their sake, he was secretly ashamed of his circumstances.
Following his Reawakening and becoming a Player, his mindset started changing with his continued combat with various creatures. He has become bolder and more confident in his abilities. At first, he was estranged from the system, being skeptical about it. As time passes, his suspicions disappear.
Background:
Jinwoo was born 20–25 years before the events of the main storyline to Sung Il-Hwan and Park Kyung-Hye and had a little sister named Jinah. Ten years before the first Double Dungeon Incident, his father was presumed dead when he mysteriously disappeared inside a dungeon during a raid. Six years later, his mother developed symptoms of Eternal Slumber and eventually fell into a coma.
With both of his parents gone, Jin-Woo was forced to take over as the family's breadwinner and went on to become a hunter. Due to how fragile he was, he quickly became a subject of mockery in the Korean hunter community and was given the disdainful nickname of "The Weakest Hunter of All Mankind." Nevertheless, he did not give up and managed to financially support himself and his sister even though he nearly died on just about every raid he went on.
D-Rank Dungeon Arc:
The dungeon Jin-Woo and the rest of the party entered turned out to be a "Double Dungeon,' meaning there was another hidden dungeon inside the dungeon they entered, which is a very rare occasion.
The Double Dungeon trapped the party inside, and the mysterious statues inside the dungeon demanded specific conditions for the party to survive. Thanks to Jin-Woo's intellect, the party satisfied the requirements.
Realizing that one person had to stay behind to keep the doors open, Jin-Woo sacrificed himself. When Jin-Woo was awaiting his death, a strange message popped up on his face saying: "You have completed all necessary requirements of the secret quest." With no time or options left, Jin-woo accepted, making him the "Player."
Reawakening Arc:
Jin-Woo wakes up in a hospital, fully healed after surviving the Double Dungeon. He notices a screen hovering above him with quest requirements written on it.
Although he did not believe it was real and ignored it, he quickly learned that it was real when he got sent to a penalty dungeon for not completing the quest on time.
As he never wanted to return to the penalty dungeon again, Jinwoo decided to take the program seriously, which he later learned was "The System." It gave him rewards every time he completed one of its quests.
After realizing he became a player in a system where he can improve his abilities and get stronger, Jin-Woo starts to grind in these virtual dungeons nonstop to get stronger and join stronger parties to be better off financially.
