Kekkaishi (結界師, Barrier master) are demon exterminators that serve as the traditional guardians of the land of Karasumori. They are trained from a very young age in the use of the Hazama-Ryu Kekkai technique, begin patrolling the grounds as early as age seven, and appear to carry out their duties until they either die or are succeeded by a younger heir (and even then, they are likely to return to action as needed). The only two active Kekkaishi families remaining are the Sumimura and Yukimura.