Japan
Japan is an island nation off the coast of east Asia. The capital city is Tokyo.
Among the guises employed by Chancellor Goth during his battle with the Fourth Doctor in the Matrix was that of a Japanese samurai. (DW: The Deadly Assassin)
The Ninth Doctor, Rose Tyler and Jack Harkness visited Kyoto, Japan in 1336. (DW: Bad Wolf)
The Seventh Doctor and Chris Cwej visited Japan in 1560. (NA: The Room With No Doors)
The Master had the TARDIS take the Eighth Doctor and Izzy Sinclair to Japan in the early 17th century, during an isolationist period, to witness the chaos being caused by the alien "Gaijin". (DWM: The Road to Hell)
The Doctor witnessed the Earth's fury at the Japanese island of Okushiri in 1720. (MA: The English Way of Death)
In 2008, a Samurai warrior was brought forward to the early 21st century by the Rift Manipulator where he began to terrorise travellers on the Tokyo subway system (TW: End of Days)
During the Year That Never Was, the Master destroyed Japan, watching the islands and its cities and inhabitants burn. However, when the year was erased from history, Japan was returned to its proper place and its people were returned to their homeland. They did not remember their own deaths or anything else that had happened. (DW: Last of the Time Lords) Martha escaped Japan and made her way towards Europe. (NSA: The Story of Martha)
During the Sontaran invasion of Earth of 2009, Tokyo was the first place of human deaths by the smog which was distributed by ATMOS. (DW: The Poison Sky)
According to Ianto Jones, Japan was one of the first countries the Daleks landed during the War in the Medusa Cascade. (DW: The Stolen Earth)
Axos took over Japan through use of ingredients in the Goruda brand drink. The children who had drank it turned into Axons. (DWM: The Golden Ones)
Due to the destabilisation of the Myloki conflict of 2066-68, Japan invaded New Zealand; by 2096 Tokyo was an independent city-state. (PDA: The Indestructible Man)