Tohsaka Rin is one of the masters of the 5th Holy Grail War. When she tried to summon a Saber-class servant, she accidentally called Archer, who is well adept in bare-handed fighting, armed combat, Magecraft, and even housework. Her failure in summoning is partially due to her lack of formal magic education, but she is considered to be extremely powerful in her own right.
Another beautiful cosplay by Kanda Midori! I wonder who she is with this time? That cosplayer looks like quite an impressive Archer. Thanks to Edwin for sending this in!