I can't argue with that...but are you certain that the sword is a weapon that suits your beliefs?

[He doesn't want Sanae going into this and regretting it, which is why he's being quite blunt here.]

It is far easier to kill then to injure and disarm. It may take years before your skills with the sword is sufficient to perform to avoid non-lethal engagements. Purifying spirits is one thing, but if your enemy turns out to be a human or some other living being, would you be willing to cut them down?