It has been passed from master to student for many years. This is how it was told to me by the reiki master.
Dr. Mikao Usui was the dean of a small Christian university in Kyoto, Japan.

One day, during a discussion with some of his students, he was asked if he believed in the literal translation of the Bible and, specifically if he believes in the miracles of healing performed by Christ.

His reply was “yes”. The next question startled Dr. Usui because they asked him things”, how come there were no more healers in the world.

Then they asked him to teach them the methods that Christ had used to heal. Bound by his honor in traditional Japanese style.

He resigned from this position as dean because he could not give them their answers. He was determined to find the answers to this great mystery and turned to the USA as the first place to seek answers to these questions. Because he was a Christian missionary and minister, he studied at the University of Chicago. During his seven years of study and in America. He tried to understand through Scripture how Jesus effected miracles and transformation. During this time. Dr. Usui receives a doctorate in theology but he did not find the revelations he was seeking.

He traveled to North Indian and Tibet since it was said that Christ had studied there. It was during this time that he learned Sanskrit.

The ancient and sacred language of the Hindus.
They studied the Tibetan Lotus Sutra and felt that he had found the intellectual answers to the mystery of Christ’s healing, but not the empowerment. Dr. Usui returned to Japan and began to focus on the Buddha. He realized that the Buddha has performed the same miracles as Jesus. He too healed the sick and had great control of energy, because he channeled the power of God and the Universe. Dr. Usui began to question the different Buddhist sects concerning their ability to perform the miracles that Buddha performed: Could they heal the body?

The Buddhists said they did not believe that the healing of the body and spirit were always directly related.

They concentrated their energy on the spirit and left the healing of the body to those concerned with the healing art.

They believed that the body and the spirit were separate and that it was the spirit that needs healing

The Japanese name for the master level of Reiki is Shinpiden which means "Mystery Teaching."

Reiki (Ray-key) is one of many complementary therapies that focus on the whole person (mind, body, and spirit) and works very well in conjunction with western medicine. These therapies enhance the body's ability to promote healing, relieve pain, reduce stress, and create relaxation, thereby improving a person's sense of overall well-being. Reiki is an intelligent energy force for healing our physical, emotional, mental, and spiritual selves. The word Reiki is Japanese and means "Universal Life Energy." Reiki is literally the life force of the universe. The Light, The Force, God, Christ, Buddha, The Great Spirit, whatever you feel most comfortable saying is Reiki. The practice of Reiki healing was discovered in the late 1800s or early 1900s by Dr. Usui in Japan.

During a Reiki session, the practitioner brings this energy to the client using a series of light-touch hand placements on (or slightly above) the body. The client (fully clothed except for shoes) usually lies on a massage or similar table. Since the Reiki energy is intelligent, it knows where to go and what to do, the energy does the healing, not the practitioner. You could experience extreme relaxation, awareness of "Inner Wisdom," emotional release, and/or clarity and insight about issues in your life, during a Reiki session. Reiki works to restore balance and harmony on all levels.

Reiki can be useful in 1) providing: relaxation, energy, and change in attitude
2) decreasing: pain, anxiety
3) promoting: health, wound healing, the release of emotion.

Reiki is Universal life-giving Energy and can be used for all purposes, conditions, and situations. It can be safely used at any time, in any place, and for anything.
To practice Reiki, no faith or belief is required. It is successfully used by people of all ages, religions, and philosophies. It is for everyone. Reiki is the most simple natural
healing method we know as a practitioner of Reiki the power of healing.

Once, a person is reawakened by a Reiki Master; with an initiation process. Then the ability to transmit this energy will be there for the rest of their lives and will flow through their hands naturally.

Energy healing promotes healing by enhancing energy flow and removing blocks in the human energy field or aura, which permeates and surrounds the body. These blockages can stem from unresolved emotional pain, past life traumas, stress or in our environment, negative thought forms, etc. Energy healing addresses the root cause of whatever issues you are dealing with so the effects are permanent.

_   It is gentle and non-invasive making it safe for everyone.
_   It works very well by itself or in conjunction with other therapies.
_   It is both beneficial in achieving and maintaining good health.
        Benefits:
            1.   Reversal of disease processes
            2.  Speed recovery from injuries
            3.  Relief from stress and trauma
            4.  Enhanced functioning of the immune system
            5.  Release from both acute and chronic pain
            6.  Improved functioning of any organ or system
            7.  Inner peace and one - near with spirit.
            8.  Stress Reduction
            9.  Relaxation physic and emotional
            10. Enhancing spiritual growth
            11.  Enhancing Immune function
            12.  Healing physical energy, experiencing inner peace
            13.  Enhancing Meditation
            14.  Energizing your home
            15.  Divine healing love helps them deepen their awareness of their innate spirituality
            16.  Nourishes your physical body and balance, mental and emotional energy.

Breathing is also one of the very important aspects of Reiki and it is something that you need to master as well.
Literally, in Japanese translated, breathing is known as the Goddess Breath Method, in which the person literally breathes down the energy towards the patient and affects their meridians.