geisha girl vs Japanese

geisha girl and Japanese both are nouns.

Word	Noun	Adjective	Verb	Adverb
geisha girl	Yes	No	No	No
Japanese	Yes	Yes	No	No

As nouns, Japanese is a hypernym of geisha girl; that is, Japanese is a word with a broader meaning than geisha girl:

geisha girl: a Japanese woman trained to entertain men with conversation and singing and dancing
Japanese: a native or inhabitant of Japan

Other hypernyms of geisha girl include Nipponese, adult female, woman.

geisha girl (noun)	Japanese (noun)
a Japanese woman trained to entertain men with conversation and singing and dancing	the language (usually considered to be Altaic) spoken by the Japanese
	a native or inhabitant of Japan

geisha girl (adjective)	Japanese (adjective)
	of or relating to or characteristic of Japan or its people or their culture or language