At "Builders Weekend 2026 Tokyo," an international hackathon held at Dragon Gate in Tokyo from March 20–22, 2026, a team joined by our CEO Takuya Tominaga won the VoiceOS Award.
About Builders Weekend
Builders Weekend is an international hackathon where programmers, designers, and marketers build a product prototype in 48 hours. 205 people took part. Digital Garage served as co-host and main sponsor, with Lovable, VoiceOS (YC X25), Supercell, RevenueCat, and ElevenLabs participating as partners. The judging panel comprised four members: Mitsumasa Kiyohara (Open Network Lab), Jerry Chi (Supercell AI Lab), Yoshi Ueda (RevenueCat), and Kai Brokering (VoiceOS).
Project Overview
We built "MissionLingo," a language-learning app for practicing real-world Japanese through conversation with AI. With three steps—Watch, Play, and Feedback—learners experience Japanese in realistic settings such as convenience stores and izakaya through conversations with AI NPCs.
In 48 hours we completed a product featuring 14 missions and 34 videos, including Live Payment Play (where "the payment itself is the lesson"), voice dialogue powered by ElevenLabs, and Kansai-dialect support.
Team
We competed as an international team of three: a Vietnamese engineer based in Japan (a winner of the previous YC hackathon), a Canadian based in Japan (an English teacher currently learning to program), and our CEO. The team formed after meeting at the ICEBREAKER NIGHT held the night before the hackathon.
Technical Highlights
- Developed two versions—a Lovable build and a Next.js build—to address every challenge
- Real payment integration via the Digital Garage VeriTrans4G SDK
- Subscription implementation via the RevenueCat SDK
- Low-latency voice dialogue using an ElevenLabs + OpenAI "TTS Race" strategy
Leach Inc. will continue to pursue the possibilities of generative AI technology through active participation in hackathons and startup communities.