|“||Ahahahahaha! Ahh, Saber. Saber. Saber. Saber! I had faith that you would come back one day! I love you. My... My prince, you belong only to me!||„|
|~ Manaka Sajyou|
Manaka Sajyou is presumably the main antagonist of Fate/Prototype. She is the older sister of Ayaka Sajyou and the former Master of Saber in the Holy Grail War preceding the one held in the events of the story. She once again participates in the current Holy Grail War, acting as the Master of Beast and the six Servants besides Saber revived from the previous Holy Grail War.
The concept behind her design was “a sense of omnipotence”. Takashi Takeuchi describes her clothing design as "super-cute." She shares a number of aspects with other TYPE-MOON characters. She is the sibling of the main protagonist and a small, pale girl who is much older than she appears like Illyasviel Von Einzbern. She is a Master from the previous Holy Grail War and shares the same Servant with Ayaka in the same manner as Kiritsugu Emiya does with Shirou Emiya. She is linked to the Root like Shiki Ryougi, and she is connected to the Grail like Sakura Matou. She was brought back to life by the Holy Grail after being killed like Kirei Kotomine. She has a low amount of circuits and high efficiency like Aoko Aozaki.
Manaka is the older sister of Ayaka, and while both were raised to be magi, Manaka was the one their father had expectations for rather than Ayaka. She participated in the Holy Grail War eight years before the main story, and was the Master of Saber. They managed to defeat the other six Masters and Servants, allowing them to finally reach the Great Grail. While her father thought he was guiding them towards a bridge to the Root that they had failed to attain for a thousand years and yearned for for a thousand years more, she had a different plan for it.
She believed such an outcome was boring, as she had already been connected to the Root since birth, so she instead decided to use it for its real purpose of raising the Beast rather than silly stories about granting wishes. She gathered sacrifices, a number of girls weeping as they fell into the Grail, and even her own father and sister. She tore her father into mincemeat, and while Ayaka could only cry and hide at the sight, Manaka easily found her and prepared to use her as a sacrifice as well. She was killed by Saber before she could do so, and unable to cope with such a betrayal, she died smiling at Saber with an expression that didn't show any pain. He threw her corpse into the Great Grail afterward.
She is a cheerful girl dead set on her dreams and completely infatuated with her former Servant, Saber, to a disturbing level. While already obsessed with him in the previous war, she has become even more unstably attracted towards him after being killed by him. She bares no hatred for him, instead referring to him as her prince, and comparing her love for him like having her organs fall out.
She can be called innocently monstrous, capable of killing her father and tearing him to pieces, and saying that Ayaka is only capable of being used as a sacrificial ingredient for the Grail simply because she is ordinary, all while smiling like an angel without any sign scorn or ill will. Her interest in obtaining the Grail is entirely for granting Saber's wish in some twisted way be manifesting the Beast. She holds no interest in reaching the Root due to her already established connection, so such a thing would have been boring.
After the defeat of Sancraid Phahn, he reveals to Ayaka that he was not one of the ranked Masters, instead taking the role of the Void extra Master, and poses the question "who is the First?" There can only be seven Masters participating in the war, so if there was to be another, it would have to be a survivor from the previous war.
After Saber uses Excalibur on Archer, Manaka begins to dance innocently like a child in the underground Great Grail in front of the currently incarnating Beast and the six Servants from the previous Holy Grail War. She begins to obsess over Saber, repeatedly calling out his name, and saying she wishes to see him soon. She claims that the Beast was born in order to make his wish come true.
Manaka is considered to be a genius Magus, and due to her superiority and Ayaka's mediocre skills, Ayaka developed a complex towards her. While she is lacking in the quantity of her Magic Circuits, their quality is beyond measurement and their composition is an abnormal, never-before-seen precedent. She has been connected to the Root ever since she was born, so she has no interest in the supposed purpose of the Grail. Its actual form is a three dimensional magic circle and natural furnace located below the city. The Greater Grail contains a black, mud-like content that looks like a sea that is slowly incarnating something on the other side. She is able to manipulate it somewhat, forming tentacles that can easily tear people apart.
Manaka's current existence, after having been thrown into the Grail, is some sort of anomaly. While she died eight years ago, she became something of a half-zombie due to the power of the Holy Grail. While she is older than Ayaka, she retains a child-like appearance. The true purpose of the Grail is to act as a cauldron of magic to give shape to the eighth Servant class, Beast. It requires sacrifice in order to form, so she used a large number of live girls, forcing them to hurl themselves into the cauldron while still conscious. Its form is the "Beast of 666" from the Bible, as the design of the Grail originates from Christianity. It refers to a beast wearing crowns symbolizing the sins and greed of humanity. It is none other than the beast that comes from the sea, written of in Revelation. She also manages to bring back the six Servants other than Saber from the previous war, and places them under her control.