The best but not perfect.

By far the best Japanese vocabulary learning app. There’s only two things it is missing which would make it perfect.
1. The option to edit the library so you can make certain kanji readings the main word, rewrite the equivalent meanings, and add new words to study that aren’t in the app, or delete redundant words.
2. The option to delete a word from a list through the search function. You can only add words this way, and sometimes it takes a long time to search through large lists to delete it from the list.