Fate/hollow ataraxia

Set in Fuyuki City, six months after Fate/stay night, Fate/hollow ataraxia follows Bazett Fraga McRemitz, a former master in the 5th Holy Grail War and member of the Mages’ Association. Her memory lost, she wakes up with Avenger, her new servant, on the fourth day of a new war. Despite her incomplete past, she is set on winning the Holy Grail War, so she and Avenger embark on their journey towards victory.
Meanwhile, Shirou Emiya is living a peaceful life with his comrades from the previous war. While Rin Toodaka travels to England to repair a faulty time and space experiment, mysterious creatures start appearing, foretelling a new danger for the Servants. In the midst of it all, Shirou meets Caren Ortensia, a mysterious young girl, when he tries to protect his loved ones.
In a repetitive time loop lasting four days, both Bazett and Shirou are trapped in the 5th Holy Grail War. With each death or survival, they gain knowledge of their previous experiences upon their return to day one. Intent on ending the cycle, they team up with Avenger to uncover the reason behind this endless repetition.