Nobita saw a moon turned yellow last night and told his class about it but they think it's funny. Doraemon gives him the "History Explorers Club Badge" and discovers there's life on the moon. Until a new student changed him forever.

Gon, a Korean hitman bred in the United States where he works for a Chinese triad, usually flawless in taking out his targets, makes a terrible mistake in fulfilling a mission. Swamped by feelings of regret, Gon no longer wants to be a hitman, but, in order to tie up loose ends, his boss forces him to do another job in Korea.

Tae-Sik is a widower with a mysterious past. When a young girl he befriends is kidnapped by a vicious drug gang, Tae-Sik rushes to save her.