It is already possible to use Japanese prompts with the KSP Android app. Currently, swiping the English keyword changes the default prompt language for that kanji to Japanese, with the kanji of interest masked. The prompt must be chosen from one of four dictionary entries, which have been farmed automatically from a publicly available dictionary of common Japanese words. The options are not always quite what you might choose if you were constructing a list of Japanese keywords. The biggest problem is the large number of homonyms in Japanese: some kanji appear in words that sound the same as other kanji, so the prompt you choose from the dictionary may not be unique. (Although the kanji itself disambiguates the definition, it is masked – a classic Catch 22.)
The final version of the app will make it possible to have one dedicated Japanese keyword for each kanji, which will appear as a kana pronunciation (as well as a kanji compound with the kanji of interest masked). This will be similar to the process described by wrightak, here:
… but with some kanji, KSP will choose Japanese keywords along the lines of the list offered here:
Both of these lists have their own issues, and no solution will please everyone, but one priority in making the KSP list will be to avoid duplicates, something not quite achieved with wrightak’s list. Matching the Japanese keyword to the English keyword will not be a priority, but KSP will note where the meanings diverge.
KSP will still be recommending that beginners start with English keywords, so that the task of assigning meaning to the visual representation of the kanji is as easy as possible, but the Android app will offer the option of switching to a Japanese prompt when the kanji is known at a specific, user-chosen level. For instance, kanji known at level 5 or higher could automatically switch to a Japanese prompt. The first time the kanji is shown after the switch, the English keyword will also be offered, but subsequently the English keyword will be suppressed. (Tapping the Japanese prompt will display a translation as well as the English keyword.)