Welcome to the Syn9 Blog

Hi — I'm Tomo.

I'm the solo developer behind Syn9, a schedule and memo sharing app. This blog is where I'll record thoughts, decisions, and releases as I build it.

What is Syn9?

In one sentence: every plan and note can be shared with exactly who you want, one by one.

• A plan you want to share with family
• A memo meant only for your partner
• A group schedule that your whole club can see

Fine-grained control over who sees what, on a per-item basis — that's the core idea. You can also chat directly about the plans and memos you've shared.

A quiet rebuild

Syn9 started out two years ago on Flutter + Firebase. In November 2025 I quietly began rebuilding it from scratch on React Native + Supabase — and that's the version you're using now.

I wrote about the full story on note (in Japanese) → スケジュール・メモ共有アプリを再構築

What you'll find here

• Thoughts I'm wrestling with as I build (product direction, design questions)
• Decisions I've made (technical choices and the reasoning behind them)
• Releases (new features and updates)

What's next

Koe — an AI feature that lets you create plans and notes just by speaking — is launching soon. I'll write a full post about how it works, and what it took to build, once it's out.

I'd be glad if even one more person comes to love Syn9 — I'd love to grow it together with all of you. Looking forward to what's ahead!