Hiroshi Kaizuka, born Koji Kaizuka on November 17, 1938, in Chiba Prefecture, was a Japanese manga artist and original creator whose career spanned from the late 1950s. He is recognized as a foundational figure in boys' manga, particularly known for his sports and action titles. His birth name is Koji Kaizuka, and he worked under the pen name Hiroshi Kaizuka.

Kaizuka's early life was marked by the loss of his father, after which he was raised by his mother. His passion for drawing emerged in middle and high school, where he formed manga clubs. After graduating, he briefly worked for the National Railways' Chiba administration office but left after six months to pursue a career in manga. He made his professional debut in 1957 as a creator of kashihon, or rental manga, with a publisher in Tokyo. The following year, 1958, he began his first serialized work, Kurikuri Pitcher, a baseball manga published in Omoshiro Book by Shueisha. This series established his reputation and began a long period of successful output.

Throughout the 1960s, Kaizuka became a prolific creator of shonen manga, with a particular focus on sports. He produced numerous baseball series, including Fight Brothers, Fastball Sun, and Lucky 9. Beyond athletics, he also wrote stories centered on World War II fighter pilots, with Zero Battle Red being among the most notable. His energetic and straightforward storytelling style earned him a reputation as a hot-blooded mangaka who could effectively speak to a young male audience.

Kaizuka played a significant role in the launch of Weekly Shonen Jump in 1968, serving as one of its featured artists and helping to establish the new magazine. His workload during this period was immense; he reportedly disappeared for a time due to overwork, during which a then-newcomer, Hiroshi Motomiya, was brought in as a substitute artist. Beyond his commercial work, Kaizuka also published a research magazine called Manga Mania, which featured his own contributions alongside those of other artists such as Tsudajiro, Yasumi Yoshizawa, and Toshio Shoji. In doing so, he acted as a mentor and provided a platform for other creators.

One of Kaizuka's major works is the manga Judo Sanka, which was adapted into a television anime that aired from April 1, 1974, to September 30, 1974. Produced by Tokyo Movie (now TMS Entertainment), the 27-episode series was broadcast on Nippon Television. The original story for the anime was credited to Ikki Kajiwara, with character designs and illustrations by Kaizuka. The series, whose title translates to Ode to Judo, follows a young protagonist from the Boso Peninsula who joins his high school judo club. The anime was the last sports-themed series from the studio that had produced Star of the Giants, and it was pulled from the air before completing its planned run due to low ratings. Despite this, it remains a documented part of 1970s sports anime history.

Hiroshi Kaizuka passed away in September 2023 at the age of 84. Through his numerous manga, his work in research and promotion of the medium, and the many assistants he trained, he is remembered as one of the most influential manga artists of the 1950s and 1960s, leaving behind a legacy as a pioneer of the sports and action genres in boys' comics.