is a Japanese manga series written and illustrated by Yuu Saiki. It has been serialized in Kodansha's manga magazine Bessatsu Friend since September 2019. A live-action film adaptation is set to premiere in Japanese theaters in June 2026.
Written and illustrated by Yuu Saiki, Yamaguchi-kun Isn't So Bad started in Kodansha's manga magazine Bessatsu Friend on September 13, 2019. The manga went on hiatus in June 2022 due to Saiki's childbirth, and resumed on July 13, 2023. Kodansha has collected its chapters into individual volumes. The first volume was released on January 10, 2020. As of December 12, 2025, twelve volumes have been released.
In July 2021, Kodansha USA announced that they have licensed the manga for English digital release in North America.
A live-action film adaptation was announced on December 6, 2025. It will be produced by Asmik Ace and directed by Saiji Yakumo, with Natsuko Takashi writing the script and Kà Âji Endà  composing the music. Asmik Ace will distribute the film and is set to premiere in Japanese theaters on June 5, 2026. The theme song is "Be My Baby" performed by Naniwa Danshi.
The series was among the top five manga in the women's category of s Electronic Comic Awards 2022.