Fate: Stay Night, Fate/Stay Night: Unlimited Blade Works, Fate: Zero, Fate: Apocrypha, Fate: Heavens Wheel, etc.
Adrien comes from a long line of mages, and is the next chosen to represent his family in the coming Holy Grail War. His chosen hero is Berserker (Hercules), the embodiment of bad luck and destruction. Adrien is ready to win no matter the cost to bring his mother back.
Marinette, who likes Adrien, finds herself thrown into the chaos when she accidentally summons Ruler (Jeanne D'Arc), the embodiment of luck and creation. Apparently the Dupain family had fought alongside Jeanne, to whom she owes a life debt from the battlefield.
Adrien and Marinette form a temporary truce to help Adrien win the grail to bring back his mother. Standing in their way are five other mages who are desperate to win for their own reasons.