Redline

A millennium ago, the Blue Moon Kingdom was engulfed in an endless war due to internal conflicts. On the verge of total destruction, the Kingdom was saved by the hands of a masked hero called the 'Red Man'. The survivors exiled the militants who started the rebellion and established the "Blue Moon City", a magnificent civilized paradise led by a large corporation.

Unfortunately, for an elementary school teacher, Mr Kim, being the descendant of the infamous tyrants meant living in the impoverished slums. Although he had nothing to his name, he held his students very close to his heart. But his life took a turn for the worst when his beloved students got kidnapped. As he took his last breath after getting shot by a gunman for attempting to save the kids, the principal of his school handed him a mask which gave him special powers. Kim, resurrected as the incarnation of insatiable, anger sets out to take revenge on the people who ruined his happy life. "I will bring my students back." Criminals beware. A teacher is coming after you to teach you regret and pain.

(Source: Kakao Webtoon, translated)