From the official website:
A legendary spy called Mr.2 becomes entangled in a mystery where a woman may not be what she says she is, and everything is more than what it seems.

MNM has long worked as a private intelligence organization that is usually deployed to countries where Korea’s direct interventions are strictly prohibited. When Mr.2, one of the top agents of the organization, is captured by his enemies while on a secret mission in a conflict zone in the Middle East, the MNM decides to abandon him in foreign and hostile territory.

Ten years later, authorities realize a doctor from the same intelligence agency has gone missing and when an explosion occurred during the rescue of the doctor, the finger is quickly pointed at someone within MNM. The Director of Intelligence even warns the MNM chief that if the case is not resolved within 10 days, the MNM organization will be disbanded and absorbed back into normal military intelligence. The team leader is advised to immediately call a man named Mystari, who no one knows is actually the legendary Mr.2. Contrary to everyone’s expectations, however, Mystari, reveals himself to be light-hearted, and is always willing to put himself on the line before anyone else. After many twists and turns, Mystari then investigates agents who are forced to retire in disgrace, one by one, regaining his reputation as a legendary spy. During the process, Sejin is captured by the enemy and learns that Sejin is actually his daughter, causing him to go into a rage of action.

Original Webtoon:
Naver Series, KakaoPage

Official Translations:
S.Chinese