[ Knives nods as Nai speaks – yes, we were born to protect our brother, that is correct – and he feels the question coming before Nai asks it. It always comes down to that woman. ]

I didn't spare her. [ He shrugs, the gesture slight. ] I have on occasion regretted that. [ It's easily half the reason Vash hates him so much. Half his hatred on behalf of eighty million human lives, and more in the following years, and the other half? Rem Saverem. ] Alone, she would have been... a good pet, shall we say, for Vash. He needs a great deal of attention, and that can be time consuming.

[ Family is the center of his world, naturally, but Vash's enthusiasm can grow tiring. It would help to have help there, and the help he currently relies on didn't prove a very comforting companion for their brother. ]

And while we're on the topic of our brother, better to know now that his gate's flow, once we finish growing, will be greater than yours. [ Which makes protecting him more difficult, because fate does have a wicked sense of humor. ] If you find yourself in conflict with him, be cautious if it becomes physical. He is stronger than you are, whether he knows it or not.

[ Which is all the more reason to keep him distracted, right? ]

It would perhaps be best to spare her.