Antoku Tennō was born in 1178. In 1080 the Antoku was proclaimed the Japanese emperor by the Taira family.
When the Antoku was an emperor, he was only two years old, so the members of the Taira family ruled Japan. But Minamoto family rejected this. And the Taira family had to leave Kyoto. The antoku was also taken with the Taira family.
But in 1085 the Minamoto's army killed all the members of the Taira family. And Antoku jumped to the sea from the ship he was on to avoid captivity. And the Antoku drowned and died.