Claude Code: My Sensei

My wife and I booked a trip to Japan. Two months out. My Japanese vocabulary: ありがとう and すみません (thank you and excuse me). That's it.

I'm not paying for another app. I already have Claude Pro. So I built a Japanese learning plugin, published it on Loooom, and I've been using Claude Code as my daily sensei. Here's how to do the same thing.

The Problem with Language Apps

Duolingo teaches you to translate sentences. Rosetta Stone drills vocabulary in isolation. Both are fine for building a base — but they won't teach you how to think in Japanese or give you a real conversation partner who can explain why a particle works the way it does.

Claude can. And if you have Claude Pro, you already have access to one of the best language tutors on the planet. You just need to give it the right instructions.

That's what the plugin does.

What Is a Claude Code Plugin?

Claude Code is Anthropic's official CLI — a terminal-based AI coding agent. But it can do a lot more than code. When you drop a SKILL.md file into .claude/skills/, Claude Code picks it up and follows those instructions in every session in that directory.

A plugin is just a well-crafted system prompt, stored as a file, installable with one command.

The Beginner Japanese Plugin

I built a 5-skill curriculum on Loooom, my open skills marketplace. Each skill is a focused lesson module:

1. 🔤 Learn Hiragana & Katakana — the two phonetic alphabets, 46 chars each, with mnemonics
2. 📐 Learn Radicals — the building blocks of kanji (~50 most common)
3. 🈁 Learn Easy Kanji — your first 50 kanji (numbers, days, basic nouns)
4. 💬 Learn Basic Conversation — greetings, survival phrases, particles
5. 🔥 Level Up — casual forms, te-form, compound sentences

Setup in 60 Seconds

You need Claude Code installed and a Claude Pro subscription.

Step 1: Create a Japanese learning directory

mkdir ~/japanese && cd ~/japanese

Step 2: Add the plugin

npx loooom add mager/beginner-japanese

This pulls all 5 skill files from Loooom and writes them to .claude/skills/. No account needed.

Step 3: Start learning

claude

Claude Code picks up the skills automatically. Tell it where you're at:

I am going to Japan in 2 months, help me prepare!

Claude loads the skill, figures out you're a beginner, and immediately gets to work. The first response asked me my level (absolute zero, picked up a few things, or studied but forgot), and without me asking, dropped my first survival phrase:

すみません (Sumimasen) — "Excuse me / Sorry / Hey, could you help me?"

Use it to get a waiter's attention. Apologize for bumping into someone on the train. Start any question with a stranger. This one phrase alone will save you a dozen awkward silences in Tokyo.

The Killer Move: Paste Your Itinerary

Here's where it gets genuinely wild. I had a rough skeleton of my trip — some days blocked off, a few must-do things. I pasted the whole thing and asked Claude to fill in the blanks.

It thought for a few minutes:

Then it created ITINERARY-2026.md — a fully structured source of truth for the trip:

For every day: specific activity suggestions with real place names, recommended timing, food picks tied to that location, Japanese phrases relevant to that day's scenarios, and booking priorities. It immediately flagged three things:

1. Book a sumo stable visit ASAP — May is a tournament month (honbasho) in Tokyo. Limited spots.
2. Hakone ryokan — the good ones with Mt. Fuji views fill up months out.
3. teamLab Borderless — books out weeks in advance.

That's a travel agent and a language tutor in a single session. And then it said: "Want to roleplay some of these scenarios? We can practice like you're already there."

Yes. Let's practice ordering ramen.

How to Trigger Each Skill

Once installed, each module is a conversation starter. Here are the prompts that work best for each:

The pattern: put yourself in a scenario. Claude plays along. You learn in context, not in a vacuum.

Bonus: Kana ASCII

While working through Hiragana I built a companion tool — kana-ascii. Claude Code runs in a terminal, so you can't render images or fancy fonts. But you can draw characters as ASCII art with stroke order baked in.

It exists as both an npm package and a Loooom skill.

CLI:

npx kana-ascii あ
npx kana-ascii aiueo       # renders あいうえお in sequence
npx kana-ascii konnichiwa  # shows こんにちわ, notes unsupported chars
npx kana-ascii AIUEO       # katakana mode

Or as a Claude Code skill (Claude draws them in-session):

npx loooom add mager/kana-ascii

Then: Draw あ for me. Show me the stroke order.

Output uses a locked dot-grid canvas — guaranteed monospace across all terminals:

あ (a) — ah as in father

. . . . . . . . . . . . .
. . - - - [1] - - - . . .
. . . . | . . | . . . . .
. . . . | [2] | . . . . .
. . . . - - - - . . . . .
. . . . . | . . . . . . .
. . . . ( . ) [3] . . . .
. . . . . . \ . . . . . .
. . . . . . ~[4] . . . . .

Strokes:
  [1] horizontal bar — left to right across top
  [2] box enclosure  — down, across, up (open top-left)
  [3] drop + loop    — down, curves into circle
  [4] hook sweep     — sweeps right, flicks up

Mnemonic: Someone tied the letter 'a' into a knot. Messy — but it IS an 'a' in there.

Weird? Yes. Memorable? Extremely. That's the whole point. It will keep getting better.

The Real Power: It Remembers You

The biggest problem with AI tutors: every session starts from zero. You explain your level, your goals, what you already know — and then next time, same thing.

The v2.0.0 update fixes this with a progress file.

At the end of every session, Claude writes your state to .claude/japanese-progress.md:

# Japanese Learning Progress

**Last session:** 2026-02-22
**Total sessions:** 1
**Trip date:** ~2 months from 2026-02-22
**Destination:** Tokyo / Kyoto

## Current Module
Module 1: Kana Foundations — in progress

## Kana Covered
### Hiragana
- あ (a) ✓ confident
- い (i) ✓ confident
- う (u) ~ learning
- え (e) ~ learning
- お (o) ~ learning

## Vocab Bank
- すみません — excuse me / sorry ✓

## Next Session
- Review: う (u), え (e), お (o)
- Continue: か row (ka ki ku ke ko)

Next session, Claude reads that file first. No recap. No re-explaining your level. You say "let's continue" and it says "Welcome back — last time you got through the vowel row. Today we're doing か."

That's a stateful tutor on your own filesystem. No account, no server, no subscription beyond what you already pay for.

Two months of sessions and you'll have a complete log of exactly what you learned, what stuck, and what to review before you land.

Level Up: Cloud Memory with mem0

The file approach has one limitation: it's stuck on one machine.

If you want to study at your desk tonight and continue on your phone on the train in Japan — you need cloud memory. That's where mem0 comes in.

Mem0 is a managed memory layer for AI apps. Free tier gives you 10,000 memories and 1,000 retrieval calls per month. A 2-month Japanese journey is maybe 600 total operations. You won't get close to the limit.

Setup (2 minutes):

1. Sign up at app.mem0.ai
2. Grab your API key from the dashboard
3. Add it to your environment:

export MEM0_API_KEY=your-key-here

That's it. The skill detects the key automatically and switches to cloud mode.

What changes: Instead of writing a markdown file, Claude calls the mem0 API at the end of every session. It passes a summary of what you covered, and mem0's AI extracts and stores what matters — kana confidence, upcoming goals, your trip date, what you struggled with. Next session, it retrieves those memories semantically and resumes exactly where you left off.

No different from your perspective. But now it works from every device where you've set MEM0_API_KEY — including the Claude mobile app when you're already in Japan.

Try It Yourself

Plugin: loooom.xyz/p/mager/beginner-japanese

npx loooom add mager/beginner-japanese

Skills are free. Forkable. You can edit any SKILL.md to customize the teaching style. If you improve it, publish it back to Loooom so others can use your version.

I'll post an update from Tokyo. Looking forward to ordering ramen without pointing.

Follow along on X for the trip.