Reiki is the name given to a system of natural healing which evolved in Japan from the experience and dedication of Dr Mikao Usui (d. 1926). Fired by a burning question, Dr Usui was inspired to develop this healing system from ancient teachings after many years of study, research and meditation. He spent the rest of his life practising and teaching Reiki. Today Reiki continues to be taught by Reiki Masters who have trained in the tradition passed down from Master to student.
There is no belief system attached to Reiki so anyone can receive or learn to give a Reiki treatment, the only prerequisite is a desire to be healed.
Reiki does not specifically target the chakras however these are useful indicaters of the condition of the aura so I do not discount them.