BOOK
#100 Days Challenge: I Built 100 Apps in 100 Days and My Life Changed published by Nikkei BP
#100 Days Challenge: I Built 100 Apps in 100 Days and My Life Changed, by author and app developer Ami Otsuka (representative of Hundreds LLC), was published by Nikkei BP. It reached bookshops on January 11, 2025. A5 format, 224 pages, 1,980 yen including tax, ISBN 978-4-296-07106-7.
The book records building one piece of software every day and posting it to X, from October 28, 2023 to February 4, 2024. Over those 100 days Otsuka typed 8,123 prompts into the AI.
Otsuka took up programming after encountering ChatGPT in a class during her final year at university. The publisher's blurb introduces the book with the line: "a lazy fourth-year student meets ChatGPT and takes up programming on a whim."
- Publication dates differ between sources. Hanmoto.com gives an in-store date of January 11, 2025; Nikkei BOOK Plus gives an issue date of January 14, 2025.
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.
