Being born into a harsh environment without knowing his parents. Castilleo had to learn how to live, learn and fight to surviving living on the streets in a highly populated city known as Demura. He was very scrawny at first and could barley fight but would always put up the effort when needed. He used to steal from a lot of stores getting punished for it or gets away by running. Also would sneak into a restaurant and sleep underneath the establishment next to the boiler to keep himself warm. This is what he basically do for his entire life until one day he wondered into the forest and was found by Rajin Monks who took him in and taught him the fighting style becoming a stronger fighter along with a friend/rival he would make named Shiro.

 Later on in life he would use his new learned skill and bring them to a well known Agency called the Royal Order where they would accept Castilleo and train him to become an Elite Hitman.

 Castilleo can be a bit grumpy at times but he will never be miserable or upset since his whole life was mostly that.


Voice Ref: https://www.youtube.com/watch?v=jK8L0hXlrF0