Fantastical 2 for both iPhone and iPad have added full Japanese localization in its latest update, which is rolling out now. Additionally, Fantastical 2 for iPhone will now let you save events as drafts.
Saving an event as a draft allows you to come back to your event or reminder later. For instance, if you're planning a party, but are still deciding on the best time for everyone, simply swipe down on your new event to save it for later.
With full Japanese localization, Fantastical 2 is now localized in six languages, the others being English, French, German, Italian, and Spanish. The update is rolling out in the App Store across the world right now, so you should be able to grab it for both devices soon.