Yamato can indeed sense the aura of death, but considering he happily kept the company of demons over humans, it wasn't enough to unnerve him - make him highly suspicious, yes, but not nervous.

"...it does, doesn't it?" Yamato said after a pause, seemingly ignoring the first question. He held the boy's gaze unflinchingly, probably staring at him too intensely, and carefully bent a fork's handle in two as easily as folding a piece of paper.

"It is my own strength," he finally replied. He wasn't lying, his magic was his strength, whether he used it for the physical of the spiritual.