Papyrus nods through the start of the explanation, because yes, that all stands to reason. Who would seek out a mysterious magic like returning the dead to life, aside from people with dead loved ones? And that kind of feeling... Well, grief could set off all kinds of decisions, and some of them not well-considered in the slightest. Just look at how morose Fluffybuns sounded, admitting his regrets. But the latter part gets the astonishment that River might be fishing for, and his eyesockets widen.

"Oho, is that why some of the humans here seem so impressed and intimidated by me?" The realization is almost a relief, because some of the attention he's been getting? This isn't the kind of fearful admiration he wants, and he'd rather it be for something he's done. His fashion, sure, but just being a skeleton happens so naturally that he could do it in his sleep, if he ever willingly slept.

"Alas! I hate to break it to you, but... I didn't masterwork necromancy myself. I grew up as a young skeleton," he explains, before narrowing his eyesockets in thought. "Unless... I skeletonized myself so young, I don't remember it... But that wouldn't explain my brother. So it's probably that I'm a skeleton monster, like any other monster."