Hanawa was born in Yorii, Saitama Prefecture. Since 1970 he worked as an illustrator. After reading the works of Yoshiharu Tsuge, he decided to switch to comic books. Hanawa's first work as a cartoonist was in 1971 with the short story "Kan no Mushi" about a boy whose mother sends him to a sadistic acupuncturist, in the alternative manga magazineGaro where he mainly worked in his career to follow. From 1992 to 1994 he drew the manga seriesTensui for Afternoon magazine, which achieved a much higher circulation than Garo and similar underground publications. Through his work for Afternoon and other mainstream magazines such as Manga Action and Super Action, he became known to a wider audience. Since 1998, Hanawa has been working for AX, the successor of Garo. In December 1994, he was arrested for illegally possessing modified model weapons and sentenced to three years in prison. Afterwards, he worked on the manga Doing Time, recalling his detention, for which he was nominated for the 2001 Osamu Tezuka Cultural Prize. This autobiographical work became a bestseller and received a film adaptation in 2002 under the direction of Yoichi Sai. Masanao Amano describes how the "outstanding realism" of the work is almost overwhelming to the reader: "Due to the documentary-like style without any sense of desire and political message is completely sucked into the work." Hanawa is sometimes considered the successor to Yoshiharu Tsuge. At the beginning of his career, he dedicated himself to the ero-guro style and created erotic-grotesque works like Akai Yoru, about a samurai who rejects his thoughts of revenge and is driven to suicide by his wife, and Niku Yashiki. Many of these works were parodies of militarism and the traditional values of Japanese culture. From the beginning of the 1980s, his manga were spiritually influenced by Buddhism and were located mainly in the Japan of the Edo and the Meiji periods and in a futuristic setting. The faces of his characters are reminiscent of Ukiyo-e; his drawings are detailed and dark. His work has been translated into English, Spanish, Portuguese, French and Italian.
