Dr. Mikao Usui rediscovered Reiki in the early 1900s, during a period of meditation in the Kurama Mountains. He discovered that he had the ability to heal without depleting his own energy.
He found that the healing techniques worked well on various ailments, and in April 1922 he opened his first school and clinic in Harajuku, Tokyo. His school/clinic was formed not just for the spiritual teachings but it was also a way for people to obtain healing. The Usui teachings included teaching people how to heal themselves (a very central point in Reiki today). Healing would be given to them, and then they would be taught how to heal themselves.
Dr. Usui found that people would often return to him after they had been healed, either with a reoccurrence of the original problem or a similar issue. He recognised the important connection between our way of thinking, or state of mind, and our physical health. He came up with the Reiki principles (Gokai) in order to help people think healthily, creating a healthier mind and body for themselves.
It is reported that he taught his system of healing to well over 2,000 people and around 15 teachers (now called Reiki Masters). One of these people was Dr. Hayashi.