Akazukin

She's a resident of Fuyuki City who died in a family suicide in Semina Apartments, whose death has become a ghost story involving "Mr. A".

In truth, the "Little Red Riding Hood" is a Supreme Mystic Code modified as a Magical Energy Reactor. In Fate/Zero, Kayneth El-Melloi Archibald chose to bring "her" with him to the Hyatt Hotel. Eventuelly the Little Red Riding Hood and Mr. A fused together becoming the individual known as Ayaka Sajyou.