It's good enough for Wikipedia
「日本研究家」の検索結果 - Wikipedia
And we do use "Japanology"—but rarely, because we use "Japanese Studies" instead. "Japanologist" is the best word in English for the word 日本研究家, but there are very few such people in the US, so we don't use it that often. We instead use words like "professor of Japanese Studies."
I think we don't use it that much also because it sounds really awkward in English. It's a weak, inelegant combination of a Germanic word and a Greek word. English tends to treat such combinations as "uneducated."
See, for example, our preference for things like "Sinology" instead of "Chinology" for "the study of China."
The problem is that English does not have a Greek prefix for "Japan" so we can't do a similar construction. We do have the non-English "Nippo-" prefix, but "Nippology" sounds weird and could be construed as racist since a racist term for the Japanese during WWII in the US was "Nips."