In January 2014, during a session with Janice Jones, a spiritual advisor I had been seeing for the previous 19 years, I was made aware of a healing energy that was more refined and contained a higher level of consciousness than anything I had previously experienced. During the session, I was given the symbol and the attunement for it and was told I was to begin teaching it as part of the ART/Master class scheduled to start the next day. The energy around this experience was so clear and powerful that I trusted what I was told and followed the instructions. The energy guided me through that first teaching experience.
The Tibetan symbols including the Tibetan Master symbol and the Tibetan Fire Serpent as well as the violet breath, were retired and replaced with the Holy Fire. (All of the Usui symbols including the Power, Mental/Emotional, Distant and Master symbols were retained.) The attunement process was changed to an Ignition for the Master level and then later a Placement process for Reiki I&II and ART. These new methods of passing on the energy were significantly different, requiring little interaction with the students, yet producing amazing results. The students experienced meaningful healing experiences and were very happy to be taking part in something so new and beneficial. This system is easier to learn and to teach and yet works better than any healing method we had been aware of.
Source: https://www.reiki.org/faqs/what-history-reiki