Yuugi didn't call it deafness. He called it selective hearing. When Yami talked, everything faded away. All that mattered was his beloved. And when he smiled that special smile, the one reserved for only him, all his troubles were gone. The world's issues blurred away when he was in Yami's arms. He was safe, deaf to the world. The tortured screams of humanity as they died always disappeared when he was in Yami's arms. Despite Yami's cruel demeanor, he was always gentle to Yuugi. No harm could come to Yuugi or the screams of the tortured would deafen the world.