PlayKatsuyo vs OpenKoto

As you play, Katsuyo analyzes the kinds of mistakes you make and feeds them to you to practice in three ways: - When you go for practice mode, it recommends targeted practice on your weakest categories (godan verbs, passive form, etc.) - The game records your mistakes and feeds them back to you in subsequent rounds of the game and checks whether progress has been made. - You can opt to do a round consisting entirely of your past mistakes, fed by a SRS algorithm. WHAT'S INSIDE • N5-N1 verb and adjectives, whose forms are chosen based on frequency of use in real conversation. • Statistics of your troublesome forms, broken down by conjugation type (e.g. passive, volitional), and word category (godan verb, i-adjective, etc.) • Practice mode which feeds you your most troublesome forms, or any combination of categories of your choice. • The Daily Five: five conjugations a day at your level, the same five for everyone, untimed. Keep your streak and accumulate "perfect days". • Timed Play rounds for pressure, untimed Study sessions for learning • Spaced repetition that quietly reschedules the forms you get wrong, so practice concentrates where it's weakest — and a Review tile on the home screen that serves the forms due today, ten at a time. • High quality voice, checked rigorously to ensure no pronunciation errors. • Full conjugation tables and plain-English explanations of the verb groups — godan, ichidan, and the irregulars • Leaderboards for every JLPT level: this week and all-time • An optional account that backs up your progress and carries it to your other devices

OpenKoto is an open-source, privacy-first language-learning app. Turn the articles, books, and videos you genuinely care about into study material, understand sentences in context, collect vocabulary, and review it on a schedule. Key features: • Paste text or import TXT, Markdown, and web content • Import TXT and EPUB books with automatic chapter splitting, in either a sentence-by-sentence view or the book's original layout • Import video and audio with SRT / VTT subtitles — or generate subtitles on device when you have none (requires iOS 26) • Subtitles follow playback sentence by sentence; tap a line to jump to it, loop a single sentence, change speed without changing pitch, and hide the text to shadow by ear • Read sentence by sentence, resume where you left off, and add bookmarks and highlights • Show word-level readings above Japanese and Chinese text (furigana / pinyin), generated entirely on device • Search the full text of everything you have imported — articles, book chapters, and media transcripts — and jump straight to the sentence • Save vocabulary, organize word packs, and use spaced-repetition review; jump from any card back to the sentence it came from • View reading and review statistics • Use the app in English, Simplified Chinese, or Japanese • Choose light, dark, and multiple visual themes • Send web pages or selected text to OpenKoto from the iOS share sheet Optional AI features use a bring-your-own-key model. Configure a compatible provider of your choice for translations and sentence explanations. API keys are stored in the iOS Keychain, while learning content and progress stay on your device. AI requests go directly from your device to your selected provider and do not pass through an OpenKoto app server. No account is required. Sample articles are included, so reading, vocabulary, and review features work without configuring an AI provider. OpenKoto is free and open source.