Do I need to install a japanese operating system.
No, unless you want to.
What kind of editor is nessasary?
Regular Microsoft World would do it.
You just need to install free Global IME for Japanese module (look in
Microsoft Downloads).
With the unicode system I can translate Katakana and Hiragana,
but no Kanji. And it is very awkward
I don't know any other way.
Katakana, Hiragana and Kanji are not different languages, but three sets
of characters constituting the united Japanese syllabo-ideographic
alphabet.
Katakana (syllabic set) is mainly used to transcribe foreign names and
terms.
Hiragana (syllabic set) is mainly used to write grammatical forms
(prefix and postfix).
Kanji (ideographic set) is used to write root words. All Kanji
hieroglyphs are taken from Chinese (but often with Japanese way to read
them).
All three sets are used together, so within one sentence from a
newspaper you usually can see a Kanji root with Katakana-transcribed
pronunciation of it and Hiragana-written ending.
The system is a bit crazy, but it works for them. And hey, what about
English spelling/reading rules? :-)
The Unicode guys did a bad job with Japanese, it's true. Instead of
making one Japanese table, they did two separate tables for Katakana and
Hiragana, and Kanji hieroglyphs you suppose to take from Chinese tables
(this is why Kanji is not listed there). Either nobody knew what the
hell he was doing, or even 64,000 Unicode positions appeared to be not
enough, so they started to save space wherever they can.
Just use the regular Japanese encoding set by default in Global IME.
This is what all your Japanese visitors will have anyway.
