The 18 Year Old Spy is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

An orphan named Hajin, trained in North Korea ever since he was little. North Korea had sent young children down to South Korea to climb up the social ladder and take high-ranked places on the social hierarchy. Hajin was chosen for this operation and was sent over. “To not be used, you must be the one that uses people from above.” Hajin did not want to be used by the North Korean government but make decisions for himself. To save his younger sister who was taken away from him, he begins to swallow up both the North and South’s organizations one by one.