The tag should be able to be applied regardless of the translation status; I second the "presented in Japanese" suggestion below.

Galleries presented in the Japanese language.

Works in Japanese, whether originally written as such or translated into Japanese.

I think this style of description is both useless and incorrect. 1. This is not how the tag is currently used, thus incorrect. Most uploads that are translated are not tagged with their 'created in' language, and this description could imply that they should be tagged as such (I'm not even against this idea, just historically it's not how things are tagged). 2. The presence of the tag under languages already describes what is proposed, it's already implied, hence useless.

@てふてふ @Hyonta すみません, でもここわくじょう お もうしたてるばしょで わ ありません です. Sorry for the stiff wording, Japanese is not my native language. An improvement from @Yoru13's version would be: "A work whose text was written in or translated to Japanese."

最近サイトが重すぎて満足に楽しめないです

最近、フタナリが多いのが気になります。 そういうジャンルが好きな人がいるのはよくわかってるつもりですが個人的には楽しめません

Just iterating, but "A work either currently in, or currently translated to the Japanese language" Otherwise, I think most of us are on the same page here.

I second Lythos, "A work made in or translated to Japanese"

I think language tags should be specific to current language, not what the source material was.

I propose 2 versions : - taken straight from the english tag : "A work made in or translated to English." - or just a simple "Moonrunes"