Maruo graduated from junior high school in March 1972 but dropped out of senior high school. At the age of 15 he moved to Tokyo and began working for a bookbinder. At 17, he made his first manga submission to "Weekly Shōnen Jump", but it was considered by the editors to be too graphic for the magazine's format and was subsequently rejected. Maruo temporarily removed himself from manga until November 1980 when he made his official debut as a manga artist in "Ribon no Kishi" (リボンの騎士) at the age of 24. It was at this stage that the young artist was finally able to pursue his artistic vision without such stringent restrictions over the visual content of his work. Two years later, his first stand-alone anthology, "Barairo no Kaibutsu" (薔薇色の怪物; Rose Colored Monster) was published.