Japan (日本, nihon) is the home country of Koei. Koei's titles are predominantly set in Japan, with most not being translated for regions outside Eastern Asia, focusing on different time periods in Japanese history.
- Ancient Japan - mythological dates; era of creation
- Heian Period - particularly the years 900–1185
- Warring States - particularly the years 1500–1615
- End of Tokugawa Regime - 1853-1869
- World War II