If you like your learning to come with a good dose of gamification and cute anime characters, then kawaii日本語 might be the Japanese learning app you're looking for. Released in 2016, it receives frequent updates and the support is very responsive, typically replying to messages within a few hours. A lot of work has clearly gone into this app, which is available in English, German, and Spanish, and while there are occasional mistakes in the English, the overall quality is good.
While kawaii日本語 is free and the ads are relatively unobtrusive, you may want to consider getting the paid version to avoid them and gain other advantages such as the ability to download lessons ahead of time. This is an advantage if your Internet connection isn't the fastest around.
The app uses a storyline to guide you through a whole range of lessons, starting with ones to teach you hiragana and katakana and then graduating on to basic grammar, kanji, vocabulary, and more. The storyline probably won't interest everyone and the music can be distracting, but if that's the case, you can simply skip the storyline pop-ups and turn off the music in the settings. Besides the lessons, there are games in the "arcade" to help you practice the points you've learned. kawaii日本語 does rely on multiple choice to a large extent and may not be the most effective way to learn Japanese. But it looks nice and is fun and fairly intuitive to use with an impressive amount of content for a free app.