Yōkwōin

Prince Masahito (, Masahito-shinnō^?, 1552–1586), also known as Prince Sanehito and posthumously named Yōkwōin daijō-tennō, was the eldest son of Emperor Ōgimachi.

Prince Masahito died before his father.

Masahito's eldest son was Imperial Prince Kazuhito (和仁親王, Kazuhito-shinnō^?, 1572–1617), who acceded to the Chrysanthemum Throne on the death of Emperor Ōgimachi. Kazuhito would become known as Emperor Go-Yōzei.

Later, Go-Yōzei elevated the rank of his father, even though his father's untimely death made this impossible in life. In this manner, Go-Yōzei himself could enjoy the polite fiction of being the son of an emperor.

The actual site of Prince Masahito's grave is known. This posthumously-elevated emperor is traditionally venerated at a memorial Shinto shrine (misasagi) at Kyoto.

The Imperial Household Agency designates this location as Yōkwōin's mausoleum. It is formally named Tsuki no wa no misasagi at Sennyū-ji.

...
Wikipedia