Tetsu Adachi is a Japanese manga artist born on February 10, 1968, in Tokyo. He began his path to becoming a creator by attending a drawing school while a student, and after graduating from high school, he briefly attended an art school but soon stopped going. He made his professional debut in 1986 after winning a新人獎 (rookie award) from Weekly Young Magazine for his work graduation album, with his first magazine serialization beginning in 1988.

Adachi has created numerous manga series, primarily for Kodansha's seinen magazines. His notable original works from this period include Sakura no Uta (serialized in Weekly Young Magazine in 1991), Weather Woman (serialized in Weekly Young Magazine from 1992 to 1994), and the comedy series Baka Kyōdai (which began serialization in Weekly Young Magazine in 1999). Weather Woman was adapted into a two-part original video animation (OVA) in 1995 and later into a live-action television drama in 1997. Baka Kyōdai, which translates to "Stupid Brother and Sister," served as the source material for the television anime Gokyōdai Monogatari, which aired from 2009 to 2010.

The creator's work on Baka Kyōdai was recognized with an Excellence Award in the Manga Division at the 17th Japan Media Arts Festival in 2003. Other notable manga by Adachi include Kira Kira! (serialized in Weekly Shōnen Magazine from 1989 to 1990), White Gift (serialized in Weekly Shōnen Magazine in 1988), and The Happiness Cloud (released in 1997). His artistic identity is rooted in seinen manga, often creating stories that blend slice-of-life narratives with elements of comedy and drama, a style that has proven adaptable for other media such as anime and live-action adaptations. Later in his career, he collaborated with writer Yōzaburō Kanari on the manga Shusendō, which was published in Shueisha's Business Jump magazine starting in December 2009.