Assessing the extent of damage quickly following a major natural disaster is crucial to ensuring that effective decisions are made to establish an appropriate first response system and implement response measures. Therefore, a real-time earthquake damage estimation system was developed. Among other things, the system estimates the distribution of seismic ground motion, structural damage, and casualties based on observation records obtained immediately after a major earthquake. In addition, the system is equipped with a function for assessing actual damage using a variety of sources and techniques. Damage estimates generated by the system were used for emergency response during actual disasters, including the 2016 Kumamoto Earthquakes, and the system’s effectiveness has been confirmed. This study evaluates the functions and performance of the system, examines its potential applications, and discusses future innovations and challenges.