In March 2011, Japan suffered devastating damage from the Great East Japan Earthquake (GEJE) and accompanying tsunami, which caused massive blackouts affecting 8.5 million customers. Damage to power stations, including Fukushima Daiichi Nuclear Power Station, caused a long-term, nationwide power shortage. Other infrastructure and customer facilities were damaged as well. Demand-side resiliency means the availability of electricity to consumers, which is an important factor that affects business continuity. Onsite generation and microgrids have been recognized as important measures that improve resiliency; successful real-life applications of these technologies, such as the Sendai Microgrid and Roppongi Hills, have increased after the GEJE. Metrics on the importance of loads or facilities and resiliency are needed to encourage investment by supporting business operators' decision making and enabling quantitative analyses of the tradeoff between cost and resiliency improvement. This paper presents a comprehensive outline of experiences and lessons learned from the GEJE from the viewpoint of demand-side resiliency-or the availability of electricity to consumers. Damage to power systems and power supply capability through power source loss, best practices (including microgrids), and post-disaster responses and lessons learned are all examined.