A key element as to why most westerners don't know about the early history of manga, other than that much of it hasn't been printed up in English, is the "fan filter". In France, where a wider variety of manga is popular, the market supports what could be called "artistic" works, and a lot of these earlier artists are a little better documented there. In the U.S., on the other hand, up until the 1990's, success of manga and anime had pretty much been limited to the west coast markets, and even then only to a negligible flow of action stories aimed at boys. Therefore, if private companies wouldn't sell translated products in America, the "next best thing" became inevitable.
That is, groups of college students, with lots of spare time and access to import stores, began fan-trading circles (both for xeroxed pages and VHS tapes). Naturally, as the fan groups reached critical mass, new companies (i.e. - Streamline Pictures, AD Visions, U.S. Manga Corps) sprang up to exploit them, which led to the release of legally licensed products in the U.S. However, the tastes of the college students initially, and the marketing decisions of the companies afterward, created "filters" that restricted the titles and artists that made their way overseas. Which means that a creator popular in Japan is completely unheard of elsewhere because specific small groups of foreign fans didn't like him/her.
Normally, "fan filters" are not an issue. Anime and manga that don't make it through the filter probably won't be well-received by anyone else in that foreign country either, and if they do become popular a new group will form to promote them. What concerns us here (or, what I want to write about and no one else wants to read) is that the filters create huge holes in our awareness of manga and anime history. Those people that were famous in Japan, but maybe not elsewhere, are the ones that helped develop the original market that we enjoy now. To understand manga history, we have to blow through the filters and look at the Japanese market directly. Unfortunately, this is difficult now since a lot of information has been lost over time, and may not be documented even in Japanese.
This is why the art exhibits at the Kawasaki and Edo-Tokyo museums, the Yayoi-Yumeji gallery and the Hongo Bunkyo cultural center are so important. Someone else has collected some of this information together for us, and with the books that accompany the exhibits, we can start patching the information back together again into some kind of Frankenstein whole.
(Illustration by Kiichi Okamoto, 1928, from Gekkan Bijutsu. Used for review purposes only.)
Kiichi Okamoto, (1888-1930), was one of the earliest shojo illustrators. From the Kodomo webpage, Okamoto was the son of the vice president of the Miyako Shimbun newspaper (later, the Tokyo Shimbun). He was educated at a western painting research institute, and became a manager of the institute in 1911 (but was expelled later when he joined a rival art group). He was in charge of binding and illustration of the Modern Family Library series in 1915, and was influenced by the art of Edmond Dulac and Arthur Rackham. In 1918, the girl's Kin no Fune (Gold Ship) magazine started up, featuring children's stories and songs, and Okamoto was commissioned to do illustrations for it. He then designed the stage art, costumes and lighting for a stage adaptation of Maurice Maeterlinck's "Blue Bird", which was sponsored by Kin no Fune. In 1922 he became Kodomo no Kuni's (Children's World) chief illustrator from its second issue; in 1923 he illustrated for Shojo Kurabu (Girl's Club); and for Children's Asahi (an Osaka magazine) in 1924. He co-founded the Japan Association of Children's Illustrators (Nihon Dogaka Kyokai) in 1927 with Takeo Takei, Shiro Kawakami, Shigeru Hatsuyama, and some others.
While he wasn't the first illustrator, as an editor and artist he definitely had a long-term impact on the appearance of early shojo magazines.