"Is the cost something detrimental to you, like will it physically injure your body or something of that nature?"
"Physically, as in will it injure me, or physically, as in, it will inhibit my future growth?" Aoni rebutted while scratching the back of his head.
To be honest, he was completely unsure how to explain away the fact that he had a mysterious resource that only he could use, and THAT was the cost of the first option.
So, instead of giving a straightforward answer, he opted to play it coy instead, something which earned him yet another swift chop to the head.
"You know exactly what I mean; stop playing dumb and spit it out." Massaging his hand because that last chop had actually fractured the bones, Anthony couldn't help but worry about his brother's future; after all, not only was he the elder brother and thus responsible for disciplining the moron, but if dum-dum Aoni kept acting this way, sooner or later it would catch up to him and be the cause of his demise.
