Fate/Zero is the story of the Fourth Holy Grail War Kiritsugu Emiya grew up wanting to be a hero who could save anyone and everyone but he learned the hard way that for every person he saved, another had to dieContain spoilers for Heaven's Feel and Fate/Zero To answer the question, first we need to understand how the Fuyuki's Holy Grail ritual really works The true mechanic behind it Not the one that being put fourth by the Three Founding Family YouFate/Zero takes place 10 years prior to the events of Fate/stay night, detailing the events of the 4th Holy Grail War in Fuyuki City The War of the Holy Grail is a contest in which seven magi summon seven Heroic Spirits to compete to obtain the power of the "Holy Grail," which grants a miracle After three inconclusive wars for the elusive Holy Grail, the Fourth War commences
Fate Zero The Fourth Holy Grail War Modern Neon Media