The Battle of Dan-no-ura was a major sea battle of the Genpei War, occurring at Dan-no-ura, in the Shimonoseki Strait off the southern tip of Honshū. On April 25, 1185, the fleet of the Minamoto clan (Genji), led by Minamoto no Yoshitsune, defeated the fleet of the Taira clan (Heike). The morning rip tide was an advantage for the Taira, but turned to their disadvantage in the afternoon. The young Emperor Antoku was one of those who died among the Taira nobles.

Taira no Tokiko was a Japanese aristocrat from the Heian period. She was the concubine of Taira no Kiyomori, mother of Taira no Tokuko, and grandmother of Emperor Antoku. Later she took the vows to become a nun, after which she was generally referred to by her Buddhist name as the "Nun of the Second Rank" .