How to add japanese characters to Writer Document?
I tried graphics to no avail.
Is there a special characters chart ?
It would help if you mention OS name, LO version and save format.
To work in Japanese, you need to enable specific features to make your life easier. Go to Tools>Options, Language Settings>Languages, tick Asian and select Japanese from the drop-down menu.
In Tools>Options, LibreOffice Writer>Basic Fonts(Asian), you can now choose your preferred font(s) in several contexts.
Basically, your question boils down to the choice of an adequate font face.
A (not that user-friendly) character chart is available with Insert>Special Character. Select first a font you know contains Japanese characters. Usually they have CJK in their name (optionally with JP). If a Japanese block is present, you can select Character block CJK Unified Ideographs (for kanji), Hiragana or Katakana.
Comprehensive charts can be found on the Unicode site.
In addition to @ajlittoz :
Have a look at templates for japanese:
https://wiki.documentfoundation.org/ReleaseNotes/24.2#Templates