You've read the title, this is Caster route. What would have happened if that night the one to save Caster had not been Kuzuki, but Shirou Emiya? Just how would Shirou change at the discovery of the Holy Grail War? How would Shirou change Caster? And how much would someone like Caster change Shirou? (Good End- Finished. True End- Work in progress)