@AsuraRaza probably more like, they are technically enemies from the start... or... its possible that
remember when he did that mana transfusion thingy which was forbidden and all that? i wonder if in doing so he turned her into a vampire (dormant) since 16.5 mentions that vampire bite is a thing in this world... maybe he like infected her mana and he will have to kill her at some point when she turns into a vampire and goes out of control?