All right, I've pushed a small fix and updated the jolla-anthy-jp package. It should be a bit better about switching to the correct input handler now. Note though that you might still have trouble getting it working in for example the browser, or at least I had, because Maliit reports 'predictionEnabled' as false for some input fields, which will cause the input handling code in jolla-keyboard to fallback on a more basic input handler. This affects not only the Japanese input method, though, but all other input methods as well.

Edit: The problem is mentioned here: https://together.jolla.com/question/...king-features/