This document discusses challenges for big data applications in Japan. It outlines three applications: 1) traffic data analysis for efficient driving, 2) traffic simulations for evacuation during earthquakes, and 3) real-time health data analysis. These could provide benefits but also invade privacy by collecting large amounts of personal data. Current law does not adequately protect privacy for data like vehicle movements. Addressing privacy concerns while enabling useful analysis will require balancing privacy protections with data use through legal and technical frameworks.