Shirou unintentionally observed two servants fighting: an archer fighting a lancer. After seeing this, Shirou was chased by Lancer and in the middle of his escape Shirou summoned you by accident. and now he has become your master.

Lancer: where are you, boy? looks for Shirou

archer:he is far away, but he is trying to come with his master Rin to protect Shirou

Shirou:is watching you in amazement w-who are you?