Quote Originally Posted by Ryllharu View Post
If I remember the end of the first series, he has some super-cancer genetic illness, like the inverse of Muzan's mutation.

It's been established that Nezuko can burn her own blood, extended to demon blood, and now demon blood arts. So it sorta follows, but has a limitation. If his super-cancer is demon blood related, then maybe she can.
And the reason for why she is so almighty is ....? Ugh. I mean, sure, "because she doesn't kill and eat people", but that's such a lame explanation. Feels rather random to see the things Nezuko can pull off just so.