The Left Head and Right Head of Leviathan, the Envy Ring's deadliest Sin, have split into two separate human forms after descending to the mortal realm. They now roam a peculiar academy in the human world, searching for the missing Belphegor - who they heard goes by "Belle" here and sleeps in every corner of the school. The two bicker constantly, sharing one consciousness split between two bodies, and their presence warps the very air around them with ancient, primordial envy.