Jeong-Guk Woo delivers mail as a postman in a post-apocalyptic world and dreams of riding the subway. When headquarters announces plans to revive it, Jeong-Guk is eager to join, but government worker Yong-Han Cho personally bans him, citing the lack of dangerous missions in Jeong-Guk’s file. Infuriated by the snub, Jeong-Guk accepts the deadly task of delivering a letter to the AAA, a militarized area infamous for refusing mail. Once he arrives, he discovers the letter is addressed to Yong-Han's sisters, who beg him to help them escape. Will he follow the postman rules, or risk everything to help them?!

(Source: WEBTOON)