This paper aims to analyze how and why Japan's new coronavirus contact tracking and tracing application has not been supported by people and in effect been ineffective in preventing the spread of infection of COVID-19. Ministry of Health, Labor and Welfare of Japan released COCOA on June 17, 2020. It has been expected to work as a platform for capturing people's close contact with infected persons. However, it is pointed out that COCOA is not working well enough despite its high expectations. In December 2019, a pneumonia case was reported in Wuhan, China. Within a few months a new infectious disease spread across the world. World Health Organization (WHO, 2020) reported in March 2020 that the disease was caused by a new virus called COVID-19. Since it takes a few days for the symptoms to appear, the virus spreads to close contacts. It is crucial to break the chain of transmission in order to cut off the route of infection. WHO suggested that contact tracing is one of the key strategies to break the chain of infection. In response to WHO advice, many countries have utilized a digital tool for tracing close contact and introduced a mobile application. The concept is to have each people install the application for monitoring its own activity. The application can trace the close contact either with the Global Positioning System (GPS) using satellites, or Bluetooth for wireless data exchange between devices. The application notifies a close contact with a person who develops symptoms once it is detected. It aims to reduce the transmission within a community, for instance, household contact, workplace, school, or public transportation. Since the application runs on the platform, network externality may work and then bring the best performance to society. That is, the more people download and the more patients register, the more effective the application will be.
