Kaku

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😭 The Problem

This project has a slightly unhinged origin story.

Years ago, I was learning Japanese and had a Japanese friend who would tease me because, despite studying the language, I could not read very well.

And... fair.

I could recognize some Japanese. I knew vocabulary. I could understand things in context. But recognizing a kanji when it was sitting in front of me was very different from actually being able to read it, remember it, and write it myself.

Then I found an Android app called KanjiTree.

KanjiTree was simple, inexpensive, and incredibly useful to me. It connected kanji recognition with vocabulary, readings, and — most importantly — handwriting practice.

Instead of only asking:

"Do you recognize this character?"

it made me actually interact with Japanese writing.

And it helped.

For the first time, I felt like I was developing Japanese literacy, rather than getting better at guessing answers on language-learning apps.

Eventually, I stopped using it.

Years passed.

Then KanjiTree disappeared from the app store.

I assumed it was just another abandoned indie app.

Fast-forward to 2026.

I'm on my way to Atlanta for RenderATL, thinking about what I might build for a Major League Hacking project. I suddenly remembered that weird little Japanese app that had helped me so much.

So I searched for KanjiTree.

And that is how, on the ride to Atlanta, I discovered that the reason my favorite kanji app disappeared was apparently much darker than a deprecated Android API:

its developer had gone to prison for murder.

That was... not the product lifecycle update I was expecting.

After processing possibly the wildest piece of software-maintenance lore I've ever encountered, I kept thinking about the app itself.

KanjiTree had been remarkably simple.

It didn't need a giant subscription.

It didn't need to turn learning Japanese into a social network.

It didn't need generative AI.

I remember paying about $9.99 for lifetime access, and that little app did something genuinely valuable for me: it helped me learn to read and write Japanese.

So I decided:

The idea deserves to survive even if the original app didn't.

That's why I started building Kaku.

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🌸 The Solution

Kaku is an affordable Japanese literacy trainer built around a simple principle:

Recognition alone is not literacy.

Knowing that 山 means "mountain" when you see it doesn't necessarily mean you can read it in a word.

And being able to read it doesn't necessarily mean you could pick up a pen and write 山 from memory.

Kaku therefore treats Japanese literacy as several connected skills:

Recognize → Read → Write → Review

Instead of giving learners one generic "mastery" score, Kaku is designed to track those abilities separately.

A learner might eventually see:

山

Recognition  ██████████  100%
Reading      ███████░░░   70%
Writing      █████░░░░░   50%

Built With

• codex
• render