Http://nihongo-app.com/ the sentences are ordered in increasing difficulty too. Source: about 1 year ago

Http://nihongo-app.com I’m surprised no one ever mentions this app. I have both Pleco and this app I linked. I don’t think I would have consistently kept up with studying Japanese for the past 3 years without this app, tbh. Pleco is awesome, but I wish the flashcard system were better. They each have their pros and cons but the app I linked has what you want and more. Source: about 1 year ago

You should check out my other app, Nihongo (https://nihongo-app.com), it has functionality like this, and is one of the reasons I developed it in the first place. I take DRM free ebooks and copy them into the app one chapter at a time. It automatically creates flashcards for all the words that appeared that I don't already know, and I can filter down to only words that appear at least twice. - Source: Hacker News / over 1 year ago

You can check out my other app Nihongo for this too (https://nihongo-app.com). :). - Source: Hacker News / over 1 year ago

I'm also a fan of learning kanji only in the context of words, and not on their own in a vacuum. I made the kanji decks in my other app Nihongo (https://nihongo-app.com) based on this philosophy. Basically, they teach you (1) the kun-yomi word(s) for each character, (2) the 1-3 most common words for each on-yomi, and (3) to write the kanji. Don't try to learn the readings in isolation, learn them in the context of... - Source: Hacker News / over 1 year ago

My friends and I also had the same problem (one of us wanted to practice Mandarin over COVID and I've studied French and Spanish and can speak neither fluently) so we created Lingoduck to chat with other language learners for free. Source: about 2 years ago