Many of Maruo’s illustrations depict graphic sex and violence and are therefore referred to as contemporary muzan-e (a subset of Japanese ukiyo-e depicting violence or other atrocities.) Maruo himself featured in a 1988 book on the subject with fellow artist Kazuichi Hanawa entitled Bloody Ukiyo-e (江戸昭和競作無惨絵英名二十八衆句), presenting their own contemporary works alongside the traditional prints of Yoshitoshi and Yoshiku.
Maruo’s nightmarish manga fall into the Japanese category of “erotic grotesque” (エログロ; “ero-guro“). The stories often take place in the early years of Showa Era Japan. Maruo also has a fascination with human oddities, deformities, birth defects, and “circus freaks.” Many such characters figure prominently in his stories and are sometimes the primary subjects of his illustrations. His most recent work is an adaption of the story “The Strange Tale of Panorama Island” by Edogawa Rampo. An English translation of this work is to be published by Last Gasp in spring 2010.