Young-gu and the Little Three Musketeers(1991)

Original title: 영구와 꼬마 삼총사

Moon Chul, Hak-gyu, and Young-ok are students in the sixth year of the National School of Life and Guidance. They have excellent academic performance, but above all, they are children who have unrighteousness and have a lingering suspicion that they cannot endure. But sometimes it's a valiant three-gunner who turns around with a miscivous joke.