Hisau, Maiya

A young woman who acts as Kiritsugu Emiya's assistant during the fourth Holy Grail War. She is cold and professional, which makes it easier for Kiritsugu to act as he needs to.

Little is known about her history, save that Kiritsugu had rescued her from a war-torn land many years ago. When Maiya was a child, she was forced into the army and trained to be a soldier. She later reveals to Irisviel von Einzbern, Kiritsugu's wife, that she had been raped by other soldiers and later lost her child. After rescuing her, Kiritsugu became Maiya's mentor and taught her his way of life.

(Source: Wikipedia)