Reiki as a method of Healing was developed by Mikao Usui and proved to be very effective in healing almost any ailment. Around the time of the 2nd world war, a Japanese woman, Hawayo Takata, living in Hawaii who had trained with one of Usui's students (Chujiro Hayashi), started sharing Reiki with the western world.
Hawayo Takata did the world a huge favour, because of her, Reiki is a well known healing technique in the western world, while in Japan, it was almost forgotten. Almost being the important word. In the late 1990's it was discovered that one of Chujiro Hayashi's other students Chiyoko Yamaguchi, was still alive, and practicing Reiki, in the way she was taught by Hayashi. Jikiden Reiki, is the name given to this style of Reiki, it is the return of the circle to the original style of Reiki, which is increadibly powerful.