KotsuKotsu Downloads & RevenueKotsuKotsu: JLPT Vocabulary · App Store

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 colour. 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 memorise words.

For every feature, we asked: “Could you still memorise 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, eve