(from Wikipedia)

A girl in Yoshina's class who used to be bright and lively but was nicknamed "The Ice Princess" after she became cold and hard-hearted. Yoshina suspects that Psyren may be the cause for Amamiya's change. Once in Psyren, she comes down with a sickness that immobilizes her. This forces Yoshina and Asaga to take care of her. Amamiya seems to know more about Psyren then the other humans that are trapped there. She also exhibits super-human reflexes when fighting 'Alfred' by saying the phrase "Raizu", her reflexes proved great enough to catch an arrow flying through the air.