KotsuKotsu: JLPT Vocabulary
Kana to N1, before you forget
Only for iPhone
Free · Designed for iPhone. Not verified for macOS.
iPhone
Two thirds of new words fade in a day. KotsuKotsu tracks each card and brings it back right before you forget. 18,557 words, kana to N1 and beyond, a day at a time.
Ever shelved a vocabulary book with the first thirty pages black with notes and the rest still spotless?
The problem isn't willpower. It's order. Nobody can tell by feel what to review and when. KotsuKotsu is a Japanese vocabulary app that works it out for you: 18,557 words from hiragana to JLPT N1 and beyond. All you have to do is today's cards.
“What should I study today?”
The app picks for you. It starts with the 208 hiragana and katakana, then runs through JLPT N5, N4, N3, N2, and N1 to words beyond the levels, in Days of 50 flashcards. Open the app and today's cards are waiting.
“I saw it once. Why didn't it stick?”
That's how memory works.
In 1885, Hermann Ebbinghaus drew the forgetting curve: two thirds or more of something new is gone within a day. But recall it right before you forget, and the curve flattens. Seeing a word once a day for ten days beats seeing it ten times in one day. This is the spacing effect, confirmed by a 2006 meta-analysis of 317 experiments from 184 papers.
“So when does it ask me again?”
The moment your chance of remembering drops to 90%.
KotsuKotsu draws a forgetting curve for every card and asks again just as the memory starts to blur. Each right answer pushes the next review out: a new word comes back in 10 minutes, a familiar one in a few days, and one you truly know in a few months. Miss it and the gap shrinks.
So your time goes to the words you don't know yet, not the ones you do, and the same 30 minutes leaves you with more.
KotsuKotsu runs on FSRS, the spaced repetition algorithm built into Anki, refined on 700 million reviews from 10,000 real learners.
“How much do I know right now?”
Every word has a temperature: where it sits on its forgetting curve, turned into a color. A word you just learned is a warm green, one you haven't seen in a while cools to orange, and one you've missed three or more times sinks to red. Scroll a word list and the gaps show at a glance.
“How far have I come?”
Track your streak and accuracy, look back on a heatmap, and see when you'll finish at your current pace.
“Why no example sentences?”
Because they don't help you memorize words.
For every feature, we asked: “Could you still memorize words without it?” Example sentences, rankings, friend lists, and logins didn't make the cut. The card holds the kanji, reading, meaning, part of speech, and word origin. That's all.
“Why no rankings?”
Because someone else's pace shouldn't become your yardstick.
New words per day, the review limit, target retention, when your day starts: you decide all of it.
There are no notifications either. Nagging alerts only make you feel chased, and an app you open that way doesn't last.
There are no accounts. Your history stays on your device, and you can export it to move to a new one.
And more
· Audio plays automatically when you flip a card
· Choose from four voices, two female and two male, and download them to listen offline
· Search by word, reading, or meaning, even in katakana or romaji
· Save the words you like and add your own notes
· Words you're forgetting and words you often miss gather in their own lists
· Words spelled the same but read differently (like 行く: いく and ゆく) link to each other in word details
· In each Day, blur readings or meanings, shuffle, or see the words you remember least first
· Menus and word meanings also come in Korean, Chinese (Traditional and Simplified), Vietnamese, Thai, Indonesian, Spanish, and French
· Browse the same vocabulary as cards at kotsu-kotsu.app/en, with history kept separate from the app
· Light and dark themes, with background effects and blur you can turn off
It's made for complete beginners starting from hiragana, test takers organizing JLPT words by level, and working adults learning Japanese on their own, without classes.
Smart is the app's job. Steady is yours.
Just finish today's cards.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
- The App Store page now lists all nine languages KotsuKotsu supports. Nothing has changed inside the app.
The developer, DONGHYEON KIM, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- DONGHYEON KIM
- Size
- 67.9 MB
- Category
- Education
- Compatibility
Requires iOS 16.4 or later.
- iPhone
Requires iOS 16.4 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
English and 8 more
- English, French, Indonesian, Korean, Simplified Chinese, Spanish, Thai, Traditional Chinese, Vietnamese
- Age Rating
4+
- 4+
- Copyright
- © 2026 JJangJJangE