Build Muscle Memory.
Write Kanji Without Hesitation.
A mastery-first writing system. No points. No streaks. No ads. One continuous, distraction-free stream that builds zero-hesitation recall — character by character, stroke by stroke.
Start Writing ✍️Beyond Gamification.
Into Mastery.
Most language apps optimize for engagement metrics — points, streaks, and leaderboards that keep you tapping, not learning. Kanji Obsession optimizes for one thing only: permanent recall.
| Typical Language Apps | Kanji Obsession |
|---|---|
| Points, XP, and leaderboards | Mastery-based progression — you advance when you can write it |
| Streak pressure and daily nags | Learn on your schedule. No guilt mechanics. |
| Banner ads and upsell pop-ups | Zero distractions. Pure writing surface. |
| Multiple choice recognition | Handwrite every character. No guessing. |
| Monthly subscription | Pay once. Own it forever. Works offline. |
| Randomized review order | Topological ordering — building blocks first |
The Component Blueprint Method
Complex Kanji are assembled from simpler ones. Kanji Obsession maps the entire writing system into a dependency graph — you always learn the building blocks before the characters that need them.
Dynamic Kana Unlocking
Before each Kanji, the app drills the Hiragana you need for its kun-yomi (Japanese reading) and the Katakana for its on-yomi (Chinese reading). Every syllabary character stays fresh in your muscle memory — whether you're a complete beginner or brushing up.
Perfect Execution, Not Self-Assessment
Most spaced repetition systems ask you to rate your own recall ("Was that Easy, Good, or Hard?"). That's unreliable. We enforce perfection instead.
Write from Memory
A character appears. You must write it — correct stroke order, correct form, from memory alone.
Hesitation Detection
Pause too long? A hint appears automatically. The system notes you weren't fluent yet.
Repeat Until Flawless
You repeat the character until you can write it without pause, without hints — pure muscle memory.
Why We Don't Use Quality Scores
Traditional SRS systems like SuperMemo-2 rely on the learner self-reporting recall quality on a 0–5 scale. This introduces subjective bias — overconfident learners advance too fast, anxious learners waste time on material they already know.
Kanji Obsession eliminates this variable entirely. We don't ask you to rate your recall. We measure it. If you can write the character from memory without hesitation, you know it. If you can't, you repeat it. The algorithm is binary: perfect or not yet.
The result is a session where every character reaches 100% execution quality before you move on. No character slips through with a "3 out of 5" rating. Every stroke is earned.
From Characters to Words — Instantly
Isolated character drills aren't enough. The moment you unlock a new Kanji, you immediately write high-frequency words that use it — cementing muscle memory in real-world context.
After mastering 日 and 本 individually, you're immediately asked to write the word 日本 (Japan). The dependency graph ensures you've already practised every component — so the word feels natural, not overwhelming.
Words are sorted into the same dependency tree as individual characters. You never encounter a word before you've mastered every Kanji it contains. This eliminates guessing and builds compound recall from the ground up.
Engineered to Respect Your Attention
Privacy-first
All data stays encrypted on your device (SQLCipher). Nothing is ever sent to us.
Offline dictionary
Full Japanese dictionary available offline. Study anywhere — no internet required.
Zero interruptions
No push notifications, no streak pressure, no study goal nags. Learn at your own pace.
Pay once, keep forever
One-time purchase unlocks advanced levels. No subscriptions, no recurring fees.
No tracking or analytics
No analytics SDKs, no ad networks, no third-party trackers of any kind.
Stroke-order practice
Write Kanji stroke by stroke with on-device handwriting recognition.
Intentional Constraints
- Paid app (no free tier beyond base content)
- No cloud sync between devices
- No social or community features
Legal Notice (Impressum)
Information according to § 5 TMG:
Dr. Markus Himmerich
Hildegard-von-Bingen-Weg 4
60439 Frankfurt am Main
Germany
Contact:
Email: support@kanjiobsession.app
The European Commission provides a platform for online dispute resolution (OS): https://ec.europa.eu/consumers/odr. We are not obliged to participate in a dispute resolution procedure before a consumer arbitration board, but we are prepared to do so in the event of a dispute.
Privacy Policy (DSGVO / GDPR)
Last updated: May 2026
1. General Information
The following information provides a simple overview of what happens to your personal data when you use the "KanjiObsession" application. Personal data is any data that can be used to identify you personally.
2. Data Collection (Local First)
Our app follows a "Privacy by Design" approach. None of your learning progress, stroke data, or search history is transmitted to us. All data is stored in an encrypted local database (SQLCipher) exclusively on your user device.
3. External Services and Third Parties
- System Text-to-Speech: The app uses the operating system's TTS engine (iOS or Android). This may involve cloud processing by Apple or Google depending on your system settings. Legal basis: Art. 6 Para. 1 lit. b DSGVO (Contract execution).
- Handwriting Recognition: We use Google ML Kit for on-device handwriting recognition. A one-time download of the recognition model from Google servers is required on first use; after that, all recognition is performed entirely on-device. No stroke data or personal input is transmitted to Google.
- App Stores: When you purchase levels, transaction data is processed by the Apple App Store or Google Play Store. We do not receive payment data.
- No Analytics: No analytics, advertising SDKs, or third-party tracking is included in this app.
4. Your Rights (DSGVO / GDPR)
Pursuant to the DSGVO, you have the following rights regarding your personal data:
- Right to information (Art. 15): You can request information about the data stored in the app.
- Right to deletion (Art. 17): Since all data is local, you can exercise this right at any time by deleting the app or clearing its data.
- Right to data portability (Art. 20): Since data is stored locally only, you have full control over your data.
- Right to lodge a complaint (Art. 77): You have the right to complain to a data protection supervisory authority. The competent authority in Germany is the Hessischer Beauftragter für Datenschutz und Informationsfreiheit.
5. Data Retention
All learning data, search history, and settings are stored locally on your device and are deleted when the app is uninstalled. We do not retain any user data on external servers.
6. International Privacy Compliance
Because this app collects no personal data and performs all processing locally, it is designed to comply with privacy regulations worldwide, including:
- CCPA (California, USA): We do not collect, sell, or share personal information as defined under the California Consumer Privacy Act.
- LGPD (Brazil): No personal data is collected, processed, or transferred internationally by this application.
- APPI (Japan): No personal information as defined under the Act on the Protection of Personal Information is acquired, used, or provided to third parties.
- PIPA (South Korea): No personal data is collected or processed by this application.
7. Age Restriction
This application is intended for users aged 13 and older. We do not knowingly collect personal information from children under 13 (in accordance with COPPA, USA). As no personal data is collected at all, no age-gated data processing occurs.
Terms of Service (AGB)
1. Scope of Service
KanjiObsession is a tool for practicing Japanese writing and vocabulary. The base version is free, while advanced levels can be unlocked via In-App Purchases (IAP).
2. Digital Content & Purchases
Purchases of additional levels are "digital content" as defined in § 356 Para. 5 BGB. Purchases are finalized through the App Store or Google Play Store, and their respective terms and conditions apply to the transaction.
For digital content, the right of withdrawal expires once the download or access to the content has begun with your explicit consent and acknowledgment that you lose your right of withdrawal upon the start of the performance (§ 356 Para. 5 BGB).
3. Warranty and Liability
The app is provided "as is" without warranty of any kind. We strive for accuracy in the Japanese data sources (JMdict, KANJIDIC2, KanjiVG, Kanjium), but cannot guarantee the correctness or completeness of the dictionary entries or learning algorithms.
Liability for damages resulting from the use of the app is limited to intent and gross negligence.
4. Intellectual Property
The software code and design are the property of Dr. Markus Himmerich. The linguistic data contained therein remains the property of the respective open-source projects (see Attribution below).
5. Governing Law
These terms are governed by the laws of the Federal Republic of Germany. For consumers within the EU, mandatory consumer protection provisions of the country of residence remain unaffected.
Data Sources & Attribution
This application relies on the following open-source projects, which provide the essential linguistic data for our learning experience:
- JMdict: Japanese-Multilingual Dictionary. Property of the Electronic Dictionary Research and Development Group. Licensed under CC BY-SA 3.0.
- KANJIDIC2: Kanji Dictionary. Property of the Electronic Dictionary Research and Development Group. Licensed under CC BY-SA 3.0.
- KanjiVG: Kanji Stroke Order Data. Created by and © Ulrich Apel. Licensed under CC BY-SA 3.0.
- Kanjium (pitch accent data): Japanese pitch accent dictionary — accents.txt. Created by Miloš Suzuki (mifunetoshiro). Licensed under CC BY-SA 4.0. Note: The source dataset was modified by normalising fullwidth characters to halfwidth, stripping grammatical part-of-speech context tags in parentheses, and mapping/merging the accent patterns with JMdict dictionary entries.
Share-Alike Data Access
In accordance with the Share-Alike (SA) requirements of the CC BY-SA 3.0 and CC BY-SA 4.0 licenses, the modified and aggregated linguistic data used in this application is made available for free to the community.
You can download the processed datasets (SQLite format) and the preprocessing tools used to generate them at our public repository:
▶ View Data Repository on GitHub
Note: Only the linguistic data and specific preprocessing scripts are subject to the Share-Alike license; the application's source code and proprietary UI design are not included.