Government of Japan
The Current Emperor of Japan (今上天皇) is Akihito. He was officially enthroned on November 12, 1990. He is styled as "His Imperial Majesty" (天皇陛下), and his reign bears the era name of Heisei (平成). Naruhito, the Crown Prince of Japan, is the heir apparent to the Chrysanthemum Throne.
Chrysanthemum Throne
According to legend, the Japanese monarchy is said to have been founded in 660 BC by Emperor Jimmu; Akihito is the 125th monarch to occupy the Chrysanthemum Throne. The extant historical records only reach back to Emperor Ōjin, who is considered to have reigned into the early 4th century. 
In the 1920s, then-Crown Prince Hirohito served as regent during several years of his father's reign, when Emperor Taishō was physically unable to fulfill his duties. However, the Prince Regent lacked the symbolic powers of the throne which he could only attain after his father's death.