After WWII
Modern manga originates in the Occupation (1945 - 1952) and post Occupation years (1952 - early 1960's), when there was a previously militaristic and ultranationalist Japan was rebuilding its political and economic infrastructure. U.S Occupation censorship policies specifically prohibited art and writing that glorified was and Japanese militarism, the policies did not prevent the publication of other types of material, including manga.
The 1947 Japanese constitution (article 21) banned all forms of censorship. this resulted in a growth of artistic creativity in this period.
In the leading of this time where two manga series and characters that influenced much of the future of manga, one is Osamu Tezuka's "Mighty Atom", otherwise known as Astro Boy in the U.S. (began in 1951), and Machiko Hasegawa's Sazae-san (Holds that longest running animated television series by Guinness World Record, the manga began in 1946, the animation began on October 5,1969 and has yet to end).
The 1947 Japanese constitution (article 21) banned all forms of censorship. this resulted in a growth of artistic creativity in this period.
In the leading of this time where two manga series and characters that influenced much of the future of manga, one is Osamu Tezuka's "Mighty Atom", otherwise known as Astro Boy in the U.S. (began in 1951), and Machiko Hasegawa's Sazae-san (Holds that longest running animated television series by Guinness World Record, the manga began in 1946, the animation began on October 5,1969 and has yet to end).
Cover if the first Astro Boy manga