The history of rugby in Japan is arguably longer than that of every major rugby-playing country in the world outside of the British Isles and Australia. Very sorry France, New Zealand and South Africa! Regarding early documented rugby history, Japan wins. Until the recent discovery of an 1864 article in a Welsh newspaper, it seemed that rugby in Japan had a longer history than club rugby in Wales, too.
Unfortunately, almost no one knows this history because Japan's rugby establishment apparently loves the story of Ginnosuke Tanaka and his friend, Edward Bramwell Clarke, introducing rugby to Keio University in 1899 so much that it dismisses rugby in the country prior to that date as mainly involving sailors and unworthy of consideration.
In 2009, this writer telephoned the World Rugby Museum (run by England's Rugby Football Union) in Twickenham to inform them of founding documented evidence of the Yokohama Foot Ball Club in 1866. An official from the RFU replied that there must be some mistake because the organization had recently researched the early history of rugby worldwide. She said a senior official in Japan re-confirmed previous information held by the RFU that rugby in the country started in 1899.