Projects / personal
Personal projects
Made for family and friends
Small tools I build outside work, for my own household and the people around me. They are hobby projects, separate from my research and teaching, and not connected to any institution I work with.
Personal · Education
おうちプリント — kids' worksheets
Printable A4 maths worksheets for elementary grades 4–5, handmade and free for any family to print. A new set every week, plus topic pages that explain each method.
Personal · Web tool
Furusato Nouzei Planner
Estimates income tax, next year's resident tax and the furusato nouzei donation limit under Japan's 2026 tax rules. It also shows when a tax-return claim costs more than one-stop because the deduction drops your income-tax bracket. For reference only, with every source cited.
Personal · Web tool
Questionnaires
Well-known psychology questionnaires to take for yourself: Big Five personality, self-esteem, wellbeing, mood, anxiety, attachment style and the dark triad. Each comes with clear charts, plain explanations and credit to the original authors. Available in English, Indonesian and Japanese.
Personal · Web app
Kasir
An offline-first cashier, purchases and daily-report app for small family businesses such as a warung or home kitchen. Each phone keeps its own records, and phones can sync through a Google Sheet. Indonesian and English.
Personal · Web app
Festival Cashier
The predecessor of Kasir, built for an Indonesian food stall at Gidaisai 2026, the Nagaoka University of Technology festival: a till, a numbered waiting list and an expense tracker shared across several phones. Kept as it was used at the event.
Before you use them
Disclaimer
Provided as is, for reference only. These are personal projects, shared free of charge with no warranty of any kind. They may contain errors and may not be kept up to date.
Not professional advice. Nothing here is medical, psychological, tax, legal, accounting, financial or educational advice, and nothing here recommends any action. The cashier apps are simple record-keeping tools, not certified point-of-sale, accounting or tax systems. Official figures always come from the relevant authority or a qualified professional.
Use at your own risk. I accept no liability for any loss, cost or penalty arising from the use of these tools.
Your data. The tools run in your browser. What you enter stays on your device, unless you turn on a tool's sync feature, which sends data only to a Google Sheet you set up yourself.
Not affiliated. These projects are not connected to Nagaoka University of Technology, Universitas Pertahanan RI, or any other organization named on these pages.
個人的に作成したツールで、無償・無保証で公開しています。医療・心理・税務・法律・会計・金融上の助言ではなく、特定の行動を勧めるものでもありません。所属機関とは関係ありません。ご利用は自己責任でお願いします。
Alat-alat ini adalah proyek pribadi, gratis dan tanpa jaminan apa pun. Bukan nasihat medis, psikologis, pajak, hukum, akuntansi, atau keuangan, dan tidak terkait dengan institusi tempat saya bekerja. Gunakan dengan risiko sendiri.
개인적으로 만든 도구로, 무료이며 어떠한 보증도 없이 공개합니다. 의료·심리·세무·법률·회계·금융 조언이 아니며 특정 행동을 권하지 않고, 소속 기관과도 관계가 없습니다. 사용에 따른 책임은 이용자에게 있습니다.