Prologue: The Red-hair Master Alteration

Ritsuka Fujimaru, Humanity's last master, or as her servant calls her Gudako has died. But, through a strange event, she was summoned into an alternate past before her journey started.
Now how does this event impact the future? well let us see

[Disclaimer]
I didn't read too much of the fate lore, so if I get something wrong, please tell me about it