Shintetsu no Agartha
真鉄のアガルタ
A mysterious infection known as Magane transforms people into corrosive iron creatures that attack and consume others. These creatures destroy entire villages without leaving survivors. Alma and his friends, who have abilities beyond normal human limits, intervene to stop them. They rescue a boy named Tenkou from becoming infected, and he joins them as a guide in their search for the fabled "Agartha of Shintetsu."