Taira no Tokiko was the wife of Taira no Kiyomori, leader of the Taira clan, and mother of Taira no Tokuko (later Kenreimon-in). As Tokuko's mother, she was the grandmother of Emperor Antoku, Tokuko's son with Emperor Takakura. Her life was deeply entwined with the Taira clan's trajectory during the Genpei War (1180–1185).

At the decisive Battle of Dan-no-ura in 1185, facing the Taira clan's imminent defeat by the Minamoto forces, Tokiko took Emperor Antoku and leaped into the sea with him, resulting in their deaths. This act was driven by her conviction that the true imperial legitimacy resided with Antoku and the Taira lineage. She reportedly assured the child emperor that the seabed would become their palace, symbolizing their undiminished sovereignty in death. Her death alongside Antoku, coupled with the loss of the Sacred Sword (one of Japan's Three Imperial Regalia), sealed the Taira clan's catastrophic downfall.

After the battle, legends arose that the Taira clan's wrath endured beyond death. A significant earthquake occurring later was interpreted by contemporaries as a supernatural manifestation of Kiyomori's spirit transformed into a vengeful dragon. This reinforced beliefs that Tokiko and Antoku resided in a royal palace beneath the sea, eternally challenging the Minamoto victory.

While Tokiko's character lacks extensive personal development or dialogue in media narratives, her actions at Dan-no-ura and their profound symbolic significance remain central to depictions of the Taira clan's demise. Her role exemplifies themes of loyalty, sacrifice, and the impermanence of power, resonating with the Buddhist ethos of the *Heike Monogatari*, where her final act underscores the clan's tragic reversal of fortune.