We have a translation thread but it's pretty much dead. Besides it's not like Kajiri Kamui Kagura where we only have japanese.
We have an official english, and the japanese only is used for supplementary materials and precisions.
Kanji are derived from chinese so that's why.
Although here we know for fact that it is used in Shintoism to refer to both Izanagi and Izanami for instance (I think the easiest example would be japanese wikipedia, which is edited by, well, japanese people).
It is used for monotheistic religions, sure, but not only.
And in Umineko, having all these Ryushiki07 explanations + instances like "best Creator", "two Creators" or the TIPS context leave no doubt on that subject.