Thread:Lord Hyōga/@comment-24940396-20140607114337/@comment-4576906-20140614221718

There is no difference in usage. Kanji is the old name for the infobox field where kanji would be displayed in the infobox; at some point the template was updated to include all types of Japanese script (ergo, Nihongo). I'm not quite sure why, since the use of katakana or hiragana scripts in an infobox are unnecessary, as all the article subjects I can think of (except for Kagome) can be represented exclusively by kanji, but there you have it.