Ryukyuan vs Nipponese

Ryukyuan and Nipponese both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ryukyuan	Yes	No	No	No
Nipponese	Yes	Yes	No	No

As nouns, Nipponese is a hypernym of Ryukyuan; that is, Nipponese is a word with a broader meaning than Ryukyuan:

Ryukyuan: a member of the Japanese people living on the Ryukyu Islands southwest of Japan
Nipponese: a native or inhabitant of Japan

Other hypernyms of Ryukyuan include Japanese.

Ryukyuan (noun)	Nipponese (noun)
the language (related to Japanese) that is spoken by the people of the Ryukyu Islands	a native or inhabitant of Japan
a member of the Japanese people living on the Ryukyu Islands southwest of Japan

Ryukyuan (adjective)	Nipponese (adjective)
	of or relating to or characteristic of Japan or its people or their culture or language