Happy Lesson is a comedy manga, written by Mutsumi Sasaki and illustrated by Shinnosuke Mori, serialized in Dengeki G's Magazine from April 1999 to September 2002, featuring a high school student who is adopted by five of his teachers. It was adapted into a five-part OVA series in 2001; a thirteen-episode animated TV series in 2002; a sequel TV series, called Happy Lesson Advance, in 2003; and a second OVA series, Happy Lesson: The Final, in 2004. The series has also been adapted into a series of drama CDs and a Dreamcast game.

Dengeki G's Magazine is a Japanese magazine published by ASCII Media Works and sold monthly on the thirtieth that primarily contains information on bishōjo games, but also includes an entire section on anime based on bishōjo games, and serializes manga and light novels based on such games. The "G's" in the title stands for "Gals" and "Games". The magazine is known for hosting reader participation games whose outcome is directly influenced by the people who read the magazine; such games include Sister Princess, and Strawberry Panic!. Dengeki G's Magazine first went on sale on 26 December 1992 with the February 1993 issue under the title Dengeki PC Engine, which changed to the current title in 2002. A special edition spin-off version called Dengeki G's Festival! is published in irregular intervals and each issue focuses on a specific bishōjo game. Four other special edition versions under the Festival! name are Dengeki G's Festival! Comic, Dengeki G's Festival! Deluxe, Dengeki G's Festival! Anime, and Dengeki Festival! Heaven. Dengeki G's Magazine's sister magazine is Dengeki Girl's Style, which publishes information on otome games, targeted towards females.