Batman

The Batman is the defender of Gotham City. As in normal canon, his civilian identity is Bruce Wayne. Batman first joined the fanfic in proper when he went to Japan on a business trip, not a day after Superman told him "Just wait 'til you someday wind up in Japan and end up getting the stuffing beat out of you by a high school girl with glasses!"

After his death, Batman will join the Fifth Holy Grail War as Berserker.

Appearances
His first appearance in Japan was entering the Daidouji mansion. He then appeared in Fuyuki city, the home of the Fuyuki Fate Knights, where he saved Illya and Miyu from a drunken pervert. However, he broke from classic plot form and did not use the 'perfect opportunity for some new character to introduce themselves dramatically by rescuing us', leaving his involvement in the matter unknown. Later, he followed the Fuyuki Fate Knights to their exposition from Kirei and then followed them back to bug their homes.

His next run-in is with Berserker, who was defeating a yakuza hideout much like Batman himself. Berserker threw him away and was gone by the time Batman returned.

Batman was present during the Fuyuki Fate Knights' battle against the Invaders.

He was also present in the battle in Uminari City, fittingly since the key point of the original battle is control over Wayne Enterprises Tower.

Trivia

 * Contrary to popular belief, Bruce Wayne dreams about solving a complex time-travel mystery with Sherlock Holmes and the Grey Ghost, who for some reason sounded like his father.
 * He does not believe Superman's "Vacation Theory" to be true.