Kyouya is conflicted hearing the choices. His face tells me he is not sure of what is going to happen once he declined. Mind wiping is a bit too vague even for him even though it is the literal meaning of what will happen to him if he declined the chance.
"I don't know... I am still unsure whether I have to do this or not. Getting my revenge on them is something but changing my whole lifestyle just for a single power is another matter."
Yami tapped Kyouya's shoulders. "We are not forcing you. We are giving you a choice whether you want to continue your normal life or throw it away and gain magic powers. You are always free to decline."
"Why do you need to wipe clean my memories? Can't I keep my memories intact without being forgotten at all?"