when diaz turned 16, he was on his way to becoming the 58th sevaar when his parents contracted a rare disease and died. later on, his younger sister elle was also infected. after losing both his parents, he would not stand by and watch his sister die. he decided to put his ambitions aside and went to fight as a mercenary so he could earn enough money to buy medicine for elle. he succeeded and was able to save elle's life, but as a result of the extra battles that he fought in, his body was greatly weakened and had to give up his dreams of becoming a sevaar. because of this, the title of 58th sevaar went to kain phalanx. elle, feeling guilty about this, decided that she would take her brother's place and become sevaar and several years later, succeeded in becoming the 59th sevaar.