English speakers will change pronunciation and spelling of foreign words to make them easier to manage and we call this Anglicization. Japanese do this too, adding extra vowels to foreign words to make them roll off the Japanese tongue more easily. Is there a word for this, like "Japanization"? All I can find is "transliteration into Japanese", but that is awkward and sounds too mechanical.
That's not quite the same as Anglicize and Anglicization, but Nipponization may suffice if you are using it in a similar context. OED mentions it can be spelled with or without an initial capital.
[Nippon is the Japanese name for Japan. Apparently Japan comes via Chinese.]