Is it true that the Japanese emperor is the only emperor in the world today?
Correct .
Japanese Emperor Naruhito is the only person in the world to hold the title of Emperor .
No other country still has a ruler or figure with a similar title—he is the “last one standing.” The Kaiser is long gone, and so is the Tsar. Naruhito stands alone, the head of a family that first entered recorded human history 2,600 years ago.
So, Naruhito’s ancestors, now 64, ruled Japan 600 years before Christ. And that lineage is fragile. His family tree is small. Only the direct male line counts—every female member of the family must leave the royal family and the line of succession upon marriage.
Only the sons of sons can succeed. Naruhito, for the record, has no sons, only a daughter. His brother has only one son. So, his nephew is the sole heir to the throne.