Fate/Zero Jump

From the introduction: In Fuyuki City, Japan, in the year 1994, a battle will rage. The 4th Holy Grail War. It will be the most brutal, unforgiving and personal conflict in the history of the Fuyuki Grail Wars, in past or future. It will not be a mess of Magi who do not understand the rules nor a chaotic brawl between the descendants of past fighters and those whose time has long since passed. The 4th Grail War will be between Magi who are terrifyingly skilled at killing, monsters who wish only to spread death and pain, nobles who have mastered the arts of magecraft and fools desperate enough to do anything to win. There is no mercy to be found.