mutex
Category: AI in Healthcare
Tokyo startup founded by University of Tokyo engineers that builds Reze, an AI SaaS that checks and automates medical claims (receipt/レセプト) billing for Japanese hospitals and clinics. mutex was founded in 2022. The company is led by Kohei Kumazawa (熊澤洸平). Based in Tokyo, Japan. Team size: 11-50. Total funding raised: $2.3M. Latest round: Series A. Key investors include MTI Ltd. (エムティーアイ), MEDIPAL Innovation Investment LPS (MEDIPAL Holdings CVC, managed with SBI Investment), Nihon Keiei (日本経営).
- Founded
- 2022
- Headquarters
- Tokyo, Japan
- Team size
- 11-50
- Total funding
- $2.3M
Value proposition
Reze imports data from existing receipt computers and EMRs. Its AI flags missed add-on fees (算定漏れ) and claim errors, manages returned (返戻) and reduced (査定) claims, and generates symptom detail notes (症状詳記). This cuts medical-office workload and protects hospital revenue. The goal is full automation of claim creation, checking and submission.
Products and solutions
Reze (AI receipt/claims support SaaS): AI receipt check, returned/reduced claim management workspace, generative-AI symptom detail note generation, diagnosis-name suggestion AI, receipt databasing and management-KPI visualization, and a closed-network plan (閉域プラン). Legacy business lines: contract application development, UI/UX design and AI solutions.
Unique value
Aims to automate the entire Japanese medical claims workflow end to end, rather than offering point checking tools. It uses generative AI and billing logic accumulated from live hospital deployments.
Target customer
Hospitals and clinics in Japan, specifically their medical affairs and billing departments (医事課) and physicians.
Industries served
Healthcare (hospital/clinic revenue cycle management, medical billing)
Technology advantage
Engineering-heavy team from the University of Tokyo, with about 40 staff who are mostly engineers. The product was developed through repeated field trials at Nagai Hospital in Mie Prefecture. It combines generative AI with structured receipt data, and it has strategic healthcare investors (MTI, MEDIPAL, Nihon Keiei) that provide distribution and domain access.
How they differentiate
Most existing tools support individual steps such as rule-based receipt checks. Reze applies generative AI across checking, returned/reduced claim management and document generation (symptom detail notes), and is moving toward fully automating claim creation, checking and submission.
Main competitors
PHC / Wemex Medicom (レセプトEye claim-checking service), AIレセチェッカー (AI receipt checker for hospitals), built-in check features of incumbent receipt computer and EMR vendors
Key partnerships
Strategic investors MTI Ltd. (エムティーアイ), MEDIPAL Holdings via its MEDIPAL Innovation CVC fund, and Nihon Keiei (日本経営, healthcare management consulting). Nagai Hospital in Mie served as the development and field-trial site. mutex is a certified IT support vendor under Japan's Digital/AI Adoption Subsidy 2026 program.
Notable customers
Nagai Hospital (永井病院, Mie Prefecture) as the field-trial and development partner
Major milestones
2022-02: Founded by University of Tokyo classmates. 2025-12: ¥60M seed round from MTI. 2026-03: Launched Reze closed-network plan. 2026-08: Certified as an IT support vendor for the Digital/AI Adoption Subsidy 2026, released returned-claim workspace feature. 2026-09: ¥281.6M Series A (cumulative ¥341.6M). 2026-10: Exhibited at the 2nd Medical DX Expo Tokyo. HQ moved to Tokyo Opera City Tower, Shinjuku.
Growth metrics
Cumulative funding of ¥341.6M. About 40 employees with an average age of about 25. Reze is in use at multiple medical institutions, and the company is expanding paid deployments. Capital stood at ¥170.81M as of September 2026.
Market positioning
Early-stage, Series A Japanese medical-DX startup in AI-driven revenue cycle and receipt automation for hospitals. It is backed by healthcare strategic investors and targets an IPO around 2030.
Geographic focus
Japan (domestic medical insurance claims system)
About Kohei Kumazawa (熊澤洸平)
University of Tokyo, Electrical/Electronic & Information Engineering. Second-time founder: co-founded a food-delivery comparison site company while at university.
Latest news about mutex
More AI in Healthcare companies
Official website: https://www.mutex-inc.dev