For each Master, a Servant. For each Servant, a Master. The relic system was never introduced, and every Master in the Grail Wars has always received a Servant based on their own personality alone. Now, the Magus Killer goes to war - and receives his greatest weapon yet. But even with all of Assassin's skill and treachery, can they stand against the raw power of the Fourth War?

The Chaldea Security Organisation... is not a thing, because they never managed to get any funding. So sad. The Wizard Marshal has offered to step in, if they'll give him a hand with these Class Cards that have been popping up all over London. Enter our bold Magical Boy, Fujimaru Ritsuka! His intrepid partner, Mash Kyrielight! And the horrible sticks making their lives hell!