The thing with this question is that it depends on what you’ve been taught by your Reiki Teacher, and what that teacher has been taught by their Reiki Teacher and so on.
For those practitioners that have been adventurous enough to study with other Reiki Teachers and/or read any of the Reiki books out there, there is still a chance that they are going to get the same story that has been told since the 1970’s, that Mikao Usui rediscovered Reiki through his studies and meditations.
When I was first interested in Reiki and wanted to learn more about it I bought a book called “Reiki for Beginners” because I thought it would be a good place to start. As I read through the chapter on the story of Reiki the author mentioned that there was a Western Reiki story that has been told ever since Reiki came through the US and out into the world and then there was a history that was evolving as more Reiki practitioners were researching the roots of the practice and of the founder in Japan.
I never paid that much attention to that chapter when I first read that book, but I am so glad that the author included that chapter. I fear that many people that are introduced to Reiki and go on to become Reiki Masters without being exposed to both the story and the researched history do a disservice to the students that they teach and the people that they introduce to Reiki.
If you have only been exposed to the Western Reiki story, then your answer to the original question is that Reiki is an ancient Tibetan practice that was rediscovered by Mikao Usui because in that story he was searching for a healing modality and through his studying of ancient scrolls and texts he was introduced to symbols and practices that only made sense to him after 21 days of fasting and meditation.
The fine folks that have researched the roots of Reiki and Mikao Usui have found many falsities within the Western Reiki story which call into question the validity of any of it.
The stories that have been passed down from Usui’s students and the association that he founded state that he was not searching for a healing modality, and that rather, he was seeking enlightenment. His three-week fast and meditation on the top of Mount Kurama was not to gain the understanding of Reiki, but instead was a preparation for death or enlightenment, whichever came first. Luckily for the world it was enlightenment.
If you are still holding on to belief that Reiki was rediscovered, then you would also have to believe that every hands-on healing modality out there (Therapeutic Touch, Healing Touch, Quantum Touch, etc.) is a rediscovered practice since healing with one’s hands has been a part of most, if not all, ancient cultures across the globe. Even during Usui’s time there were many healing groups in Japan and he may have studied with some of them according to different authors.
What Usui did was to create a system, not hands-on healing. The system he created was called Shin Shin Kaizen Usui Reiki Ryoho which translates as Usui’s Reiki Healing Art for The Improvement of Body and Mind. The Reiki symbols were not ancient symbols from Tibet that he magically understood on the mountaintop. The techniques that he taught to be used in Reiki sessions were unique and different than other healing modalities at the time and before, and some of these have not continued to be taught in the Reiki classes that have continued once the practice left Japan.
And so if the original question I posed was regarding the Reiki practice, then I hold to the fact that Usui created the Reiki system of healing.
If you are interested more in the history of Reiki and Mikao Usui I suggest you check out the following books:
This is Reiki by Frank Arjava Petter
The Reiki Sourcebook by Bronwen and Franz Stiene
If you’re interested in the evolution of Reiki since Usui’s time check out:
Reiki Systems of the World by Oliver Klatt