Set up a Japanese input source on Mac
If you set up the Hiragana, Katakana, or Romaji input mode, you can type in Japanese.
On your Mac, choose Apple menu
in the sidebar. (You may need to scroll down.)Go to Text Input on the right, click Edit, then in the dialog that appears, click the Add button
in the sidebar.Select Japanese from the list of languages on the left (use the search field or scroll down), then select any of the following on the right:
Japanese - Kana
Japanese - Romaji
Tip: The Romaji typing method is useful when you’re not using a Japanese keyboard; text you type is automatically converted to hiragana.
Click Add.
After you add a Japanese input source, you can change settings, for example, to select input modes or show predictive text completion candidates.
Note: If your Mac has a Touch Bar, you can customize the Control Strip by adding the Input Sources button 
. See Customize the Touch Bar.