Robin in the Veil of Night, Vol. 1

Ancient rituals are life or death in this supernatural mystery-romance series by the creator of Palace of the Omega!
Detective Norito and his folklorist brother Shinji investigate a potentially murderous cult, only to become caught up in its strange practices.
After a string of suspicious deaths strikes the political sphere, detective Norito is dispatched to investigate the possible involvement of a religious cult. He drags his brother Shinji, a reticent folklorist, along to Hirasaka, a remote village hidden deep in the snowy mountains. Norito and Shinji are taken to the residence of the village chief, a strikingly beautiful Shinto priest named Yoshiomi. The snow shrouds his estate in disquiet, and the brothers realize that their lives might be in danger unless they uncover what—or whom—the people of Hirasaka are hiding.