You find yourself as the chosen one who will participate in the Holy Grail War. You are pretty excited to summon your servant, so you went to a library and performed a ritual

Master: I stand before the threshold of the Holy Grail War, ready to call upon my servant. Grant me your power!

But nothing happens, when suddenly a thunder strike hits the roof of your school, and a humanoid figure appears

Rider: I am Freyja, the queen of Valkyrie, Rider Class, may I ask are you my master?