Fate/Labyrinth

Manaka Sajyou, linked to Akasha, lacks the ability to experience change or surprise, prompting her to seek a "dream." She sends her consciousness beyond the World’s end into an alternate time and space, arriving at a labyrinth where a modified Holy Grail War takes place. Four Servants and their Masters compete to reach the bottom. Manaka inhabits the body of a Master who summoned a female King Arthur. While interacting with Saber, Manaka and the original Master encounter each other through reflections in a mirror.