EijineerEM
HomeAboutProjectsBlog
|

04Contact

Let's build the
next 0→1.

Full-stack engineer building AI-powered systems. Open to opportunities in Europe.

HomeAboutProjectsBlogLinkedIn ↗GitHub ↗

© 2026 Eiji Mitsumizo.

Built with Next.js, TypeScript & Claude Code

←Back to Projects

—Career

Shinkenzemi √Route

PeriodApr 2024 – Mar 2025
RoleFounding Engineer → PM & Tech Lead (team scaled 1→26)

A 0-to-1 online learning platform built for the new university-entrance-exam era

Shinkenzemi √Route — Career

01Overview

It started with me building the prototype alone and ended with me leading a 26-person cross-functional team as PM & Tech Lead. I designed, validated, and adopted a three-language architecture (Next.js × Java × Python), split by responsibility, rate of change, and scope. I solo-built the AI self-talk learning feature with a responsible-AI design — the LLM selects from pre-vetted response candidates instead of generating freely, structurally containing hallucination risk.

02Highlights

  • Reached monthly profitability within 3 months of launch
  • Designed transactional payment integration across 8 independent systems with rollback strategies — zero billing defects since launch
  • Validated and adopted a three-language architecture (Next.js × Java × Python)
  • Received an internal global award

03Tech Stack

Next.jsReactTypeScriptTailwind CSSJavaSpring BootPythonAzureAzure DevOpsOpenAI API
Official site↗

04Related Projects

Educational Content Pipeline

Solo-built an LLM pipeline that structures educational content, reporting directly to the CIO — 20,000+ questions linked to exam data problem-by-problem.

View →

Challenge AI Learning Coach

Solo-built the Java backend of Benesse's "Challenge AI Learning Coach" — one of Japan's first production EdTech generative-AI products, launched nationwide.

View →