CocoaInput

It is the mod which enables you to input MultiByteCharacters(IME) in Minecraft on Mac OS X naturally.
Now,it is released between 1.7.10 and 1.9.
(There is some possibility of working not enough on Chinese and Korean in 1.7.10 and 1.8.x)
Download page (required:forge)
License:Minecraft Mod Public License Japanese Transration

Google日本語入力

ことえりライブ変換

搜狗中文拼音输入法