Tengu Barai no Sankyoudai

Mamoru Yamaemori is cursed to fight terrifying Tengu alone, and he will sacrifice everything to keep his two younger brothers safe. He spends his days tending his family shrine in the mountains of Japan and battling the flesh-eating creatures, determined that his brothers will never inherit his duty. Mamoru believes his life is already decided: bound by his parents and a sinister ceremony involving Tengu blood, he is destined to die young while serving others. To protect his family, he must balance his role as a caring older brother with the mindless beast he becomes in battle—or risk turning into the very monster he fights.