皇こう太たい孫そん

noun

eldest grandson of an emperor in the line of succession

A formal imperial title; used in historical and modern contexts for the eldest grandson of the reigning emperor who is heir apparent.

• 皇こう太たい孫そんは天皇てんのうの長ちょう男なんの長ちょう男なんにあたる。

  The Kōtaison is the eldest son of the Emperor's eldest son.