Okuninushi (大国主) is a Kunitsukami and former ruler of Izumo, until Ninigi took over. In compensation he was made ruler of the unseen realm of spirits and magic. He's said to be the God of Nation-building, Business, and Medicine.
"A terrestrial deity and descendant of Susanowo, he is an important god in Japanese Izumo mythology. He is a peaceful god who prefers not to fight."
—Shin Megami Tensei III: Nocturne Compendium
Devil Summoner : Raidou Kuzunoha vs. King AbaddonEdit
Okuninushi appears in a special Case File pitting Raidou against several of the bosses of the previous game. He is the leader of a stray squad of Yomi-Kugutsu, and, possessed by the undying fury of the Kunitsukami, seeks to stamp out the servants of their rivals, the Amatsukami, and establish a land of the dead; he is also particularly angry about the defeat of his close friend Sukuna-Hikona.
Once defeated, the malevolent desire will fade away, but he establishes the Kunitsukami's grudge is still latent, and asks Raidou to purge it from other deities who might be possessed by the bloodlust.
Okuninushi appears in Amane's 8th day route as an antagonist and final boss. Unwilling to leave Japan in the hands of the Messiah, he threatens to destroy the nation and rebuild it anew unless the protagonist can fulfill his terms: to guide the first murderer, Cain/Naoya, to salvation as a sign of worth.
During the final battle, he revives twice due to the power of his mother. After the second revival, Naoya arrives and places a barrier to prevent him from reviving. Upon his defeat, Okuninushi agrees to abdicate Japan to the protagonist. He will be unlocked for fusion upon continuing from a Clear Save.