Tsunomaru is a Japanese manga artist born on May 27, 1970, in Chiba Prefecture, Japan. His real name is Masaaki Tsuno. He made his professional debut in 1991 with the one-shot Go Go Pocho Mukin, which was published in Weekly Shonen Jump and received a newcomer’s award from the magazine. His first serialized work, Mon Mon Mon, ran in Weekly Shonen Jump from 1992 to 1993.

Tsunomaru is best known for creating the horse-racing comedy Midori no Makibaō, which was serialized in Weekly Shonen Jump from 1994 to 1998. The series follows the journey of a small, unusual horse named Makibaō who strives to become a champion racehorse. This work was adapted into a 61-episode anime television series, solidifying his reputation as a prominent creator in the industry. The manga received the 1997 Shogakukan Manga Award in the children's category.

Following the success of Midori no Makibaō, Tsunomaru continued to create works for Shueisha's publications. His subsequent serializations in Weekly Shonen Jump include Survibee (1999), Jūshin Igari Tora Jirō (2001), and Gocchan desu!! (2003–2004). After departing from Weekly Shonen Jump, he shifted to other magazines, creating series such as Taiyō no Makibaō (2007–2011) and its sequel Taiyō no Makibaō W (2011–2016) for Weekly Playboy, continuing the story of the original Makibaō universe.

His artistic identity is characterized by a distinct and somewhat unconventional drawing style. Many of his characters feature monkey-like facial expressions, with small eyes, large nostrils, and prominent lips, a style that was particularly evident in his early work Mon Mon Mon. He is also recognized for his deep interest in horse racing, a theme that permeates his most famous works, and for incorporating his love of punk rock music into character names. In 2018, he published a short series titled Gag Manga-ka Ningen Dokku Death Race, in which he publicly disclosed that he had been diagnosed with multiple cerebral ischemic lesions.