Tatsuhiko Yamagami was born on December 13, 1947, in Tokushima Prefecture and was raised in Osaka. His professional debut as a manga artist came in 1965 with the work Himitsu Shirei 0, published during his time working at the Hinomaru Bunko publishing house, which was known for its rental manga. In 1970, he achieved his first serialization with Hikaru Kaze, a work that marked his early engagement with gekiga and science fiction, addressing themes rooted in contemporary political realities such as the Vietnam War. Following this period, he transitioned from these serious tones to specialize in gag manga, a move that would define his career.

Yamagami is best known as the original creator of the manga Gaki Deka, which was serialized in Weekly Shonen Champion from 1974 to 1980. The series, a slapstick comedy centered on a self-proclaimed boy police officer named Koman, became a massive success, with its compiled volumes selling over 30 million copies. The work’s popularity led to two anime adaptations. A 22-episode television anime series produced by Gallop aired on Fuji TV from October 1989 to March 1990. Concurrently, a three-episode original video animation produced by Daiei Film was released in November 1989. Decades later, Yamagami authored a sequel manga titled Nakaharu Koko-kun, which was serialized in Big Comic from 2004 to 2009.

After a period of inactivity stemming from a desire to focus on novel writing, Yamagami returned to manga. In the 2010s, he collaborated with artist Mikio Igarashi to create the suspense manga Hitsuji no Ki, serialized in Evening magazine from June 2011 to April 2014. This work, which he wrote while Igarashi provided the art, garnered critical acclaim, winning an Excellence Award in the Manga Division at the 18th Japan Media Arts Festival in 2014. It was later adapted into a live-action film released in February 2018.

Yamagami’s artistic identity is marked by a distinct evolution from politically and philosophically inclined gekiga to becoming a central figure in Japanese gag and parody manga. His work in the 1970s was considered part of a counter-cultural youth movement, and he was hailed as the reigning champion of comedy manga, with Gaki Deka credited for boosting the circulation of its publishing magazine significantly and introducing a new type of comedic hero. Throughout his career, he also mentored several future notable manga artists. In addition to his manga work, he has worked as a novelist.