Boy and Kimba the White Lion. Tezuka was inspired by American cartoons, and pioneered the so-called "story manga": long-running manga series with a cinematic style and continuity across multiple chapters, contrasting what had previously been a medium defined by one-off comic strips. Science fiction stories about robots, space travel, and heroic space-faring adventures enjoyed popularity during this period; many sci-fi stories took themes and concepts from war comics and re-imagined them with pacifist ideals, such as Tetsujin 28-go by Mitsuteru Yokoyama. One of the first new manga magazines of the post-war period was Manga Shōnen, which launched in 1947 and published works by Tezuka, Leiji Matsumoto, and Shōtarō Ishinomori. As post-war censorship codes were repealed and Japan entered a period of significant economic development in the 1950s, sales of manga and the number of manga magazines increased significantly, and and manga came to further establish themselves as distinct categories. The first works of sports manga also emerged from manga during this time; notable early works include by Eiichi Fukui as the first manga series in the genre, and Ashita no Joe by Asao Takamori and Tetsuya Chiba, which became one of the most commercially successful works in the genre. 1959 saw the launch of Shōnen Sunday and Weekly Shōnen Magazine, the first weekly manga magazines. Other weeklies, such as Shōnen Champion, Shōnen King, and Shōnen Ace, emerged in the 1960s. Weekly Shōnen Jump was first published in 1968, and would establish itself as the best-selling manga magazine across demographic categories, a position it holds to this day. Many of the most popular and commercially successful series originated in Weekly Shōnen Jump, including Dragon Ball by Akira Toriyama, Naruto by Masashi Kishimoto, Bleach by Tite Kubo, One Piece by Eiichiro Oda, and Slam Dunk by Takehiko Inoue. Modern era manga became formalized as a category of manga aimed at an older male audience in the late 1960s and early 1970s, and many artists associated with the realist movement migrated to manga. The demise of the (rental manga) market led many artists to move into magazine publishing, including manga, bringing their distinct themes and style with them. As a result, manga came to deal with more serious and political themes, and saw an increase in depictions of violent and explicit subjects, as well as an increase in profanity. Significant artists of this era include Shigeru Mizuki, creator of the horror series GeGeGe