Cover of the magazine Ukiyo (うきよ), 11/1921. (Found here)
The word ukiyo is probably familiar to many in the compound ukiyo-e, "images of the floating world". Ukiyo means thus floating world, but the cover reveals through subtle hints that this is a new world - the old-time bijin (美人 - "beautiful person", the female subject-object of countless ukiyo-e woodcuts) has changed into a modern girl (モダンガール), a waitress at a Western-style café.
(Waitresses at Café Printemps, 1922; source)
That is my guess; the little clues consist of her laced apron combined with a fresh blush, a matching comb and a coquettish gesture. She resembles the Taisho era popular image of the café waitress, which still lives on in Japanese pop culture. For a basic introduction to the café boom in 1910's and 1920's Japan, see Elise K. Tipton's article "Pink Collar Work" in the excellent journal Intersections: Gender, History and Culture in the Asian Context.
(Two Taisho era waitresses; more images here)
In some ways, the café waitresses carried on the geisha tradition of providing inspiring company, selling a romantic fantasy over a cup of coffee or tea. Because they were associated with modernity and Westernization, but perhaps even more because their customers were poor students and aspiring intellectuals, the waitresses were often ridiculed and depicted as prostitutes (and some of them doubtlessly had to be; their salaries were extremely low, and Tipton has some interesting stories about waitresses trying to organize themselves and join the labour movement). (Some examples of cartoons here.) Today, the "maid café" fad plays on similar strings - it is the fleeting dream that is desirable, not the fulfillment of desires. In this case, nostalgia enhances the value of the fantasy. Because the 21st century waitress is no longer a threat to the social order, the early 20th century waitress is seen as an innocent and plucky character in a historical romance. She is even desirable (and marketable) as a costume, like other characters from bygone times: the samurai, the ninja, the courtier.
A Taisho waitress costume from a contemporary costume rental service.