To define erotic manga, a definition for manga is needed. While the "Hokusai Manga" uses the term "manga" in its title, it does not depict the story-telling aspect common to modern manga, as the images are unrelated. Due to the influence of pornographic photographs in the 19th and 20th centuries, the manga artwork was depicted by realistic characters. Osamu Tezuka helped define the modern look and form of manga, and was later proclaimed as the "God of Manga". His debut work "New Treasure Island" was released in 1947 as a comic book through Ikuei Publishing and sold over 400,000 copies, though it was the popularity of Tezuka's "Astro Boy", "Metropolis", and "Jungle Emperor" manga that would come to define the media. This story-driven manga style is distinctly unique from comic strips like "Sazae-san", and story-driven works came to dominate "shōjo" and "shōnen" magazines.