Reiki is an ancient healing practice that was rediscovered by Mikao Usui in Japan during the 1920s. Since then, it has been spread and taught throughout the world, and there are now many different systems and types of Reiki available. The traditional Usui system of Reiki follows the lineage of Mikao Usui, in which the energy is passed from teacher to student through an attunement process, maintaining the authenticity and integrity of the practice.