There have been many systems of Reiki healing but do not have a lineage going back to Usui Sensei. Mikao Usui Sensei was the founder of the Usui Reiki healing system in the 1920’s. His method to improve body and spirit was originally designed for the individual then evolved to treat others in his clinics. The Reiki was aiming to not only cure disease but to correct the mind by a God-sent spiritual ability to keep the body healthy and enjoy a welfare of life. The five admonitions recited daily: Don’t get angry, Don’t be grievous, Express your thanks, Be diligent in business, Be kind to others.
Dr. Chujiro Hayashi a student of Usui, became a Reiki Master in 1925 and initiated 13 masters.
Ms. Hawayo Takata received her mastership form Dr. Hayashi in 1938 and trained 22 Reikii Masters in the United States and Canada.
Reiki is passed on from Master to Student through attunements and lineage.
• There are at least 600,000 Reiki Masters in the world today, with 4,000,000 practitioners. Anyone can learn Reiki.
• There are three basic levels of Reiki training and advanced.
• Level one certification (most common) is especially used by caregivers.
• One who receives Reiki training is able to give treatments to themselves, others, and any living thing.
https://www.reiki.org/faq/historyofreiki.html