This... are they parodying something? Yes the blond girl *could* be Fate but it seems off, and yes the pink haired girl could be Caro but the hair is too long and the suit makes no sense and the boy could be Elio but again it just doesn't seem to be and the hair color is wrong...

So, are they cosplaying something or is this something completely different?

Eve, from Black Cat?

Its not Fate, thats for sure. For one thing, Fate's fingers don't turn into knives...