PRODUCT
Ami Otsuka completes #100 Days Challenge: 100 consecutive days of building and posting software
Ami Otsuka (now an author and representative of Hundreds LLC) built one piece of software a day and posted it to X for the 100 days from October 28, 2023 to February 4, 2024. Games, bots, tools: 100 consecutive days.
Over the period she used 8,123 prompts, kept 300 pages of notes, and worked roughly ten hours a day. At the outset each piece was expected to take two or three hours.
The record of those 100 days led to the book #100 Days Challenge (Nikkei BP), presentations at international conferences, and the founding of Hundreds LLC.
Links書籍情報（日経BOOKプラス）ASCII.jp インタビューX
- Sources differ on the start date. The book and the JEPA slides say October 28, 2023; the Mac Fan Portal article says October 27, 2023.
About Ami Otsuka
Author and app developer; representative of Hundreds LLC. Starting in October 2023, while a student at Chuo University, she built an app a day with ChatGPT for 100 consecutive days and posted each one to X, a record published as #100 Days Challenge: I Built 100 Apps in 100 Days and My Life Changed (Nikkei BP, 2025). Named to Forbes JAPAN's Women In Tech 30 in 2026. She is now based in Thailand, writing, speaking and building apps.
