The story takes place in an alternate timeline of the original "Fate/stay night" series. It follows Shirou Emiya and his friends as they deal with a new threat in the form of a mysterious organization known as the "Mafia".
"Fate/Strange Fake" is a light novel series written by Hikaru Muno and illustrated by Takashi Takeuchi. It's a spin-off of the popular "Fate/stay night" series.