An early start

An Early Start » by Aria6 In one particular timeline, Uryuu Ryuunosuke picks the wrong house and draws the summoning circle in the blood of the living. So by accident the Servant he summons isn't for him, but for a young Emiya Shirou. How will this change the course of the Fourth Holy Grail War? Some Servant and class swaps. (you can find it on fanfiction.net)