Because it’s a common Japanese school uniform. Why you’re seeing a bunch of them is another question, but they’re not actually dressed like Donald Duck purposely.
The sailor fuku (セーラー服, sērā fuku) (lit. ‘sailor outfit’) is a common style of uniform worn by female middle school students, traditionally by high school students, and occasionally, elementary school students. It was introduced as a school uniform in 1920 at Heian Jogakuin (平安女学院)[9] and 1921 by the principal of Fukuoka Jo Gakuin University (福岡女学院),[10] Elizabeth Lee. It was modeled after the uniform used by the British Royal Navy at the time, which Lee had experienced as an exchange student in the United Kingdom.
Why am I seeing a whole bunch of pictures of female Japanese adolescents dressed like Donald Duck?
Because it’s a common Japanese school uniform. Why you’re seeing a bunch of them is another question, but they’re not actually dressed like Donald Duck purposely.
Is it related to WW2 era navy uniforms, like Donald Duck’s? Or is it some freak convergence?
https://en.wikipedia.org/wiki/School_uniforms_in_Japan
I believe so. They actually are called “sailor” uniforms.