KakaoTalk, now indispensable in daily life, first launched in 2010. Thanks to its innovative feature of free messaging on smartphones, it spread like wildfire, gradually replacing traditional SMS text messages. It was the moment when text messaging, a core revenue source for mobile carriers, became obsolete, overtaken by instant messaging services using data networks. I vividly remember KakaoTalk rapidly increasing its user base with its distinctive notification sound, automatically adding friends, and supporting group chats.

Since then, numerous instant messaging services launched globally, competing fiercely. Among them, ‘LINE’ uniquely gained explosive popularity not in Korea but in Japan. It became Japan’s national messenger app, particularly cementing its image as a reliable service for emergency communication during the Great East Japan Earthquake. Though it started as a Japanese subsidiary of Naver, it has now become a core pillar of a giant IT group through a management integration with Z Holdings, a subsidiary of Japan’s SoftBank.

Through this book, I gained detailed insight into LINE’s successful growth journey. Encountering the management philosophy and development process of former CEO Akira Morikawa led me to redefine **‘Simple’**. It taught me the thought process of a **PM (Product Manager)**, prompting reflection on what to discard and what to choose when creating a ‘blockbuster product’ – the essence of business. Given the nature of the software I sell, I frequently meet with PMs at client companies. This book was immensely helpful in understanding their work methods, roles within their organizations, and their actual needs. Specifically, by helping me grasp the gap between technology-focused developers and market-value-focused PMs, it provided valuable advice for strengthening my ability to support both roles simultaneously and drive business development.

Seeing the author’s career journey—starting at a major Japanese broadcaster and building a career pursuing his dream of music—made me realize he was a courageous figure who challenged Japan’s past ‘lifetime employment’ culture. It made me realize that innovators with a startup spirit exist everywhere in the world, and his perspective on the changes in Japan’s internet industry and market was fascinating. Starting from a small game development team and building a national app, I was reminded that behind this success were ‘extraordinary’ people. To become such an extraordinary person myself, I rise at 4:30 AM every day to start my day and keep records.