It's fall, which means a new Pokemon game was released! As with the last few entries into the series, it's very easy to change your in-game language to Japanese when you start the system.
Even better, you can choose between kana or kana plus kanji. If you've ever played games in Japanese, you probably already know that playing one entirely in kana when you're more advanced is just as much of a nightmare as playing one with all kanji when you're a beginner. But Pokemon lets you choose based on your skill level.
Another plus is that there is a ton of katakana. I often see Japanese self-learners having a hard time getting used to katakana, especially if they haven't recently been to or lived in Japan. But the truth is, katakana is important and Pokemon can teach it in a way that's not only interesting, but good for your memory!
Why? Because many Pokemon moves are written in katakana and Pokemon share a lot of moves (for the most part). So you'll be reading things like マジカルリーフ (Magical Leaf) and ハイドロポンプ (Hydro Pump) and オーロラビーム (Aurora Beam) over and over, until you don't have trouble reading katakana anymore.
And if you read it wrong you'll probably start losing. You can't use １０まんボルト on a ground type. Geez.
If you're already a fan of Pokemon, there's no excuse for you to not be playing in Japanese at this point. Keep a notebook or an SRS app open to add words to your normal study method as you play and learn a bunch of neat new vocabulary!