Zachary, a loner, is gifted a divine dog, Lucky, by a mysterious immortal. Unbeknownst to all, Lucky is a descendant of the Heavenly Devourer, bound by a God-Binding Chain. When greedy thieves steal Lucky and break the chain, a demonized Lucky awakens, unleashing a bloody rampage for vengeance. Amid the chaos, only Zachary's bond can calm the beast. Their ordeal draws the attention of the secretive Bureau 749, who recruits the unique duo for a new chapter.
