Records of heads of state
Officially, the current Emperor of Japan, Akihito is the 125th in line from the first emperor Jimmu, who is variously believed to have reigned in the 1st or 7th century BC. The earliest documentary evidence is only for the 29th emperor, Kinmei (AD 509–571); however, this is sufficient such that even the most conservative of estimates still places the Japanese imperial family as among the oldest lines in the world today.
Pretender
Since 1911, the Japanese government has declared the southern claimants were actually the rightful emperors despite the fact that all subsequent emperors including the then-Emperor Meiji were descended from the Northern Court, reasoning the Southern Court retained possession of the Three Sacred Treasures, thus converting the emperors of the former Northern court into mere pretenders. In other words, six former emperors of the Northern Court have been counted as pretenders instead since then. As a result of this compromise, the present Japanese Imperial Family is descended of the Northern Court Emperors.