@dunavin lol So true. However, now that we've actually got to see a bit of the Barbarian culture, we can see that the women are normal people(at least where the little sis is concerned). Hell, they even mention that there are normal civilians among the Barbarians. Hopefully, as you said, the MC takes note of this and sees that not all Barbarians are soldiers ripe for the slaughter now that he has experienced their society first-hand. (though, this isn't odd...even in real life, we all demonize or vilify our enemies)
Yeah, it is pretty stupid. I suppose they(the Barbarians) figured they'd keep her protected at all times as she's so important...oops. >.< lol (Come to think of it...did they even take her body after they killed her? What's the use of killing her if you don't even claim her body to have access to the tattoo...or did they skin her back..? Now who's the barbarian... :/ lol) Well, as has been said constantly...they're known for their brawn, not their brains.