Mikao Usui grew up at a time when Japanese society and culture was going through a period of rapid change. It was not until the 1850s that Japan opened itself up to the Western world; for two centuries starting in 1641, all Europeans except the Dutch had been expelled from Japan. Those Chinese and Dutch that remained were confined in special trading centres in Nagasaki, and no Japanese were allowed to leave the country. 

Christianity was declared illegal and all Japanese were forced to register at Shinto temples. Those Japanese who refused to renounce Christianity were executed, and so were a few Christian missionaries who refused to leave the country. This ban on Christianity was not lifted until 1873. 

It was the United States that finally forced Japan to open its borders, and open its economy, to the outside world, and this event led to a great flood of new ideas and esoteric systems coming into Japan from all over the world. Not only that, but Japan underwent a period of rapid industrialisation, transforming itself from a feudal society into an industrialised nation - able to compete with the West on an equal footing - within a period of only 30-40 years. Such a period of rapid change created a real climate of 'wanting to keep hold of traditional culture'. 

Japan was looking for a spiritual direction and people wanted to rekindle and maintain ancient traditions, while embracing the new. This is what Usui did when he developed Reiki. In the time when Usui was growing up, Japan was a melting pot of new ideas, with many new spiritual systems and healing techniques being developed. Reiki was one of these systems.