Kaguya Clan

The Kaguya clan (かぐや一族, Kaguya Ichizoku) is known to be very barbaric. Only a fairly small amount of members possess the Kekkai Genkai Shikotsumyaku and have fully mastered its use. The clan is very savage and have no tactics when going to battle, tenacious enough to back down even when surrounded and completely outmatched, preferring to fight to the death for fun.

Apparently, the members who possess the Shikotsumyaku abilities have a different bodily structure, meaning medicine used for regular [human] patients may have absolutely no effect on the latter.