Emperor of Japan
The current Emperor on the throne is typically referred to as "Tennō Heika" (, "His (Imperial) Majesty the Emperor"), "Kinjō Heika" (, "His Current Majesty") or simply "Tennō", when speaking Japanese. The current Emperor will be renamed "Daijō Tennō" (, Retired Emperor), often shortened to "Jōkō" (), upon his planned retirement on 30 April 2019, and renamed "Heisei Tennō" () after his death and will then be referred to exclusively by that name in Japanese. In Japanese culture, it is considered a major faux pas to refer to a living Emperor by his posthumous name, although the posthumous name is the same as the era, which is used in official documents.
Emperor Kōmei
Emperor Kōmei was the last Japanese Emperor who had more than one era name ("nengō") during a single ruling term. Beginning with his successor, Emperor Meiji, a single era name (identical to the Emperor's official title) was selected and did not change until his death. There were seven "nengō" during Kōmei's reign.