Upon assuming leadership of the Port Mafia, Ougai Mori tasks the young Osamu Dazai with delving into the enigmatic whispers surrounding 'Arahabaki.' This elusive entity appears linked to Mori's late predecessor, a connection he wishes to remain concealed. In his pursuit, Dazai crosses paths with Chuuya Nakahara, a wielder of gravity manipulation and head of the youthful Sheep gang. While their future holds the promise of becoming the notorious duo, Twin Dark, they must first navigate their conflicting personalities to unravel the secrets shrouding this compelling puzzle.