Reaper of the Drifting Moon

Pyo Wol was an orphan who wandered around the continent until he bumped into a mysterious man and lost consciousness. When he wakes up, he finds himself in a dark, confined space with only one iron door for an exit. Wol survives the next several grueling months, trying to keep a cool head and stay in shape. When the iron door finally opens, he discovers he's not the only one in this miserable situation. A group of masked people has kidnapped 300 children to train them into human weapons. Wol must fight and kill the others, for only a handful of the strongest will be selected. Will Wol be able to become one of the chosen and find a way to free himself from his captors?

He’s in the deepest part of the Jianghu. Keep your eyes wide open if you do not wish to get dragged into the abyss.

Kidnapped children raised 7 years in darkness for a single assassination mission that goes awry.