Japan’s monarchy is the oldest continuous hereditary monarchy in the world. It is also the last country in the world that is still formally an empire. The imperial dynasty started with emperor Jimmu in 660 BC and continues today with the current emperor, Akihito. You can find both of these emperors locking the Japanese emperors family tree.
Japanese passport shows the Imperial Seal on the front cover, the symbol used by the Japanese Imperial family from the early days of the dynasty.