[1][2][3] Alternative manga originated in the lending libraries of post-war Japan, which charged a small fee for borrowing books.
The market was notorious amongst parental groups for containing more lewd content than the normal mainstream manga publishers would allow.
As gekiga gained popularity, the lending libraries gradually collapsed due to the growing economy of Japan during the 1960s.
At around the same time gekiga elements began appearing in mainstream manga magazines, with Osamu Tezuka fully embracing the style and doing more work aimed at older audiences.
Magazines like Morning and Afternoon published artists who had styles reminiscent of the then-considered "retro" alternative manga from the 1960s and 1970s.