The one who obtains the Holy Grail will have any wish come true.

The Holy Grail War. A great ritual that materializes the greatest holy artifact, the Holy Grail. There are two conditions to participate in this ritual: to be a magus, and to be a "Master" chosen by the Holy Grail.

There are seven chosen Masters, and seven classes of Servants; beings akin to superhumans with incredible fighting abilities. There is only one Holy Grail. If you wish for a miracle, prove that you are the strongest with your powers.

Emiya Shirou is a high school student who has learned rudimentary magic from his father and uses it to fix objects. He finds himself engaged in the Holy Grail war as he gets attacked by a Servant. As he gets cornered, he somehow summons his own Servant and manages to stay alive long enough to compete against the other Masters.