The diamond panthers : The orphans' origins

rumors of monsters existing have always been told by the old people of the village,but those are just kid's tales right?Ash and Willow are twins living in a village enclosed by a wall,no one has left the village for 200 years,apparently the wall is to keep the monsters out,when monsters invade and whole village destroyed Willow and Ash deiced to become monster hunters,meeting countless friends along the way.