3x1 - The Familiar of Zero

Saito's runes disappear before his, Louise's and Siesta's eyes. While on a trip to the castle, they are attacked by Sheffield, who is revealed to be the familiar of an unseen Void mage that she refers to as "Master Joseph". After arriving at the castle, Saito is given a paper by the princess that would make him a knight and effectively a noble. He, however, turns it down on the issue that he does not believe he can protect the princess or Lousie without the familiar's contract. When asked about the disappearing runes, he tells them about the elf, whom he recalls as Tiffania. Derflinger tells them where they may find her so Louise and Saito prepare to depart. That night while worrying about recent events, Louise awakens to find Saito awake outside on the balcony. She tells him that she is afraid of him leaving again, especially with the disappearance of the runes. He reassures he will not leave despite the absence of any contract. However, when he tries to have sex with her, she blows him up.