Ayaka's older sister who fought and died as Saber's Master during the previous Holy Grail War. Highly regarded as a genius magus, her father had great expectations for her to win the War and to bring her family ever closer to the Root. Her level of talent would cause Ayaka (who had little talent for magecraft) to develop a superiority complex towards her. Over the course of the War Manaka would become attached to her Servant to the point of obsession, discussing the War and the Grail itself as they fought together.

It would be later revealed that she had no intention of using the Grail's wish-granting power to reach the Root as her father desired. Having been born with a connection to the Root itself, Manaka would find her father's goal of reaching the Root "boring" and would instead offer human sacrifices to the Grail in an effort to raise the "Beast" (the Beast from the Book of Revelations), fulfilling the original purpose of Heaven's Feel (The Holy Grail War) to begin with. Realizing her true intentions and dark methods however, her Servant would stab her from behind at the end of the War, barely saving Ayaka from being sacrificed as their father already had and watching Manaka die with a smile on her face, unable to understand his betrayal. After her death he would throw her body into the Grail, ending the War with no victor.

As the next Holy Grail War began Manaka would be resurrected by the power of the Grail as the 1st Master of the War, Seraphim, becoming the final antagonist of the story with the Beast itself as her Servant. Despite her death by his very hand she would become even more obsessed with Saber, calling him her "Prince" and expecting him to come back to her.

(Source: TYPE-MOON Wikia)