Reiki was founded by Mr. Mikao Usui (臼井甕男) in 1922 in Japan. After working in a variety of jobs such as a journalist and as a secretary for the politician Shinpei Goto (後藤新平), and owning his own trade company, Mr. Usui retired and began training his mind at a Zen temple in search of understanding the world (in Buddhism, this is referred to as enlightenment 悟りを開く) and discovering the purpose of life (安心立命_Anjinryumei). "安心" translates to 'no worry', while "立命" means holding your mind fulfilling that which is given from the universe. One should maintain calmness of mind, unaffected by surrounding influences, and embrace a heavenly feeling at all times, controlling one's mind without confusion amidst the influx of meaningless information or fear of death.

However, it wasn’t easy to find what he hoped for. Then he sought  the consulting with the great Zen teacher. He was told, "Try to face your own death," and so he decided to fast on Kurama Mountain. Twenty days passed, and suddenly he felt a sensation like lightning striking his head and penetrating his body's center, causing him to faint. Upon awakening, he felt refreshed and calm, experiencing a sense of satisfaction. He then decided to descend the mountain, marking the 21st day since he began fasting. On his way down, he tripped and injured his toes, causing a nail to come off and bleeding to occur. He applied his hands to the injury, and miraculously, the bleeding stopped within minutes, and the pain disappeared. At the base of Mt. Kurama, there was a diner where he had his first meal after fasting for 20 days. When he looked at the waiter, who had a horrible toothache and a swollen cheek, Mr. Usui applied his hands, relieving the pain completely and reducing the swelling. It was then that he realized his ability of the hands, which he called "Reiki."

Usui established own Reiki clinic in Harajyuku Tokyo in April 1922.

On September 12th, 1923, a great earthquake struck the Kanto area, including Tokyo, causing a widespread conflagration. Everywhere, there were cries of pain from the wounded. Mr. Usui felt pity for them, and every morning he went out to roam the town, treating these casualties free of charge. He cured and saved innumerable people.

He trained 21 teachers capable of giving attunement in 4 years. One of these teachers was Mr. Tyujiro Hayasi (林忠次郎), a Navy doctor. Hayashi taught Hawayo Takata (高田ハワヨ), who lived in Hawaii, USA, as a second-generation Japanese American. From there, Reiki spread to the entire world.