Sousei No Onmyouji

Briefly about Sousei No Onmyouji manga:

Two kids, Rokuro and Benio, are destined to be onmyouji warriors. Their lives are connected to the power of the spirit world, and their job is to fight against yōkai that come out at night. One day in summer, Rokuro returns home from school to find his house surrounded by yōkai... He quickly realizes that he alone can't defeat them, so he sets off with his sword looking for Benio "The Two must combine their power and become the strongest!"'''