What about women? While some may be stealing glances at the magazines of their brothers, boyfriends, or husbands, probably few would want to buy an erotic comic magazine for themselves. Eroticism for females, particularly in girls' comics, is couched in the softer tones of romance. Yet perhaps the best illustration of the Japanese tolerance of fantasy, and of the unique dichotomy between fantasy and reality, is in stories of male homosexual love, currently popular among young girls.
While most of the stories appear in regular girls' comic magazines, one of the largest publishers of erotic comics in Japan, San Shuppan, also issues a magazine called Junè, featuring mainly stories of love between beautiful teenage boys overseas, drawn by women artists. the target readership is junior and senior high school girls. Why are sweet, naive Japanese girls interested in such a seemingly decadent subject? As an editor at San Shuppan says, "At that age in Japan, most girls, in fact most boys, have very little to do with the opposite sex, but they have a great deal of curiosity. Love between boys in another country is so completely distant from their own reality that it's not threatening, yet it still gives them a vicarious experience. They also think it is pretty."
The ukiyo-e woodcuts of the Edo period during the Tokugawa shogunate (1603-1868) are often considered the spiritual ancestors of contemporary manga comics (and associated light novels, original video animations, anime, etc.), but the cultural syntax of the two forms is very different, and there's a touch of discontinuity in trying to draw a direct line of descent.
It is true both ukiyo-e and manga include a subset of erotic materials, some of which are implicitly or explicitly homosexual in nature. Japanese cultural norms regarding age of consent, acceptable depictions of childhood nudity in art, and censorship of erotic works underwent a considerable (one might argue forced) evolution between the end of the Tokugawa shogunate and the assumption of the 1947 Constitution adopted after the military victory and occupation of the United States; American comic books strongly inspired Japan's own home-grown comic book tradition, which has continued to grow and involve to match the local audience and creators.
Which is a long way to say, you weren't seeing young school girls in Edo in the 17th century buying erotic woodcuts of underage boys in homosexual relationships. That market didn't exist, the women who write and draw that material didn't exist (which isn't to say there weren't female ukiyo-e artists or a female audience for erotic prints, just that the combination of factors wasn't there).
Schodt suggests that the particular censorship issues of the Japanese government - namely, the prohibition on depiction uncensored genitalia and pubic hair - directly led the emphasis on perceptibly "younger" subjects in erotic comics:
Whatever the original motivation, in the 1980s traditional erotic manga for adult men (often referred to in the industry as sanryū gekiga, or "third-rate graphic novels") gradually gave way to erotic manga with a rorikon [lolicon, from the novel Lolita dealing with pedophilia] flavor. Instead of adult males doing very adult things to mature women (neighbor's wives, waitresses, office workers, buxom foreigners, that sort of thing), the sex objects became increasingly "cute"--and younger. That more and more women, who tended to draw characters in a "cuter" style anyway, were entering the erotic comic market certainly accelerated the phenomenon.
The implication of this is that instead of erotic comics being made primarily for an adult audience of pedophiles or homosexuals, the Japanese censorship standards encouraged artists to move toward characters that appeared culturally younger and "cuter," and with an audience of a broader range of ages and tastes, in large part because Japanese comics enjoyed a broader appeal among both children and adults. This is especially true for "boy's love" stories in comics aimed primarily at women, and by women creators. And it didn't happen right away, the marketing of comics for women and by women really only took off after World War II.
[...] by 1976, the first same-sex bed scene between two bishōnen appeared, drawn by Takeimya Keiko in Kaze to ki no uta (The Song of the Wind and the Trees). [Matthew] Thorn had observed that what was characteristic of bishōnen stories produced in the late seventies was that "pure love between boys" was a "beautiful thing" whether or not it was expressed physically, but that sex for the sake of lust was "something dirty". By the late seventies the representation of sexual activity in shojō manga [manga for women] had thus already been detached from the confines of heterosexual conjugal relations, but the proper use of sex was still firmly attached to love.
So it was a gradual thing, not something imported wholesale by ukiyo-e, but developed over time as the cultural conditions of Japan created a demand and allowed a space for women to both read and consume this kind of fiction.