Assumptions
- Japan-domestic B2B customer focus
- 1–3 people, post-seed
- Monthly SaaS budget under ¥50k
- Invoice System compliance required
Core
**Support/CRM**: Channel.io (Japan) + LINE Official Account **Business cards/leads**: Sansan (or personal Eight) **Accounting/tax**: freee (Invoice System + 年末調整 native) **Team messenger**: Slack or Chatwork **Project**: Backlog **Docs**: Notion **AI**: Claude Pro + ChatGPT + ELYZA + Notta **Automation**: Yoom (strong Japanese SaaS integrations) **Payments**: Stripe Japan or PAY.JP **HR (on hire)**: freee HR or SmartHR **Tax accountant**: ¥10–30k/month
Monthly cost
- Channel.io + LINE: free–¥5,000
- Sansan: Eight personal free / Sansan from ¥10,000/month
- freee: ¥2,000–4,000/month
- Slack/Chatwork: free–¥500–850/user/month
- Notion Team: $10/month
- Claude Pro + ChatGPT: $40
- Yoom: free–
- Tax accountant: ¥10–30k/month
About ¥30–50k/month total.
Pitfalls
- Starting without Sansan: business-card Excel bomb
- Delaying Invoice System registration: post-Oct 2023, your buyers can't claim input tax — they suffer
- Slack-only: hard to communicate externally with Japanese customers (pair with Chatwork)
Japanese startup spine: freee + Sansan + LINE.