Uonuma Usui

Usui, the Blind Sword, used to be a swordsman working for the shogunate government. However, in a fight against Shishio Makoto, he was blinded. He possesses the Shingan (Eye of Heart), which actually is superhuman hearing that lets him hear another's heartbeat thus enabling him to sense people around him and detect the emotions of others. This ability is so advanced that it appears to be similar to the sonar of a dolphin or bat. Usui and Shishio made a deal upon Usui joining the Juppongatana: That Usui could try to kill Shishio anytime he gets the chance.