Learn Italian: Lui è giapponese e abita in Giappone. - He is Japanese and lives in Japan.

In Italian, adjectives of nationality (like giapponese) and languages are not capitalized. However, the names of the countries themselves (like Giappone) are proper nouns and must start with a capital letter.

Would the word giapponese change if we were talking about a woman?

No, it would stay exactly the same. Italian adjectives that end in -e in the singular, like giapponese, are used for both masculine and feminine subjects. If we were talking about a plural group, it would change to giapponesi.

Why do we use the preposition in for "in Japan"?

You always use the preposition in before the names of countries, regions, and continents in Italian. If you were talking about living in a specific city instead, you would use the preposition a (for example, abita a Tokyo).

Could I leave out the word Lui and just start with È giapponese?

Yes! In Italian, you can usually drop subject pronouns like lui (he) or io (I) because the verb form already tells us who the subject is. Including Lui here just adds a little emphasis or clarifies who is being talked about.