xNurikox
Well the main idea behind it is that they're two people connected by fate. Like a soul mate or something similar. But only strong units can control spells and fight together and I think that's why the school was created, so that strong fighters could develop their spells and techniques. But who can say if the school is the actually source behind their power?. I personally don’t believe anyone made and gave the powers to a number of specific units; I think it all comes down to the strength of the fighter. But let’s put it this way - in a world where virgins have cat ears and tails anything can be possible so the possibilities behind the reason and connection of fighter and sacrifices are endless (well they're actually all in the author's head...)
Yes but what brought on the whole fighter and sacrifice unit? we know what they put them their for, but we dont know why they put them there for!