"An evil Manikin that was reborn, called back into the world by the Afterlife Bell. Because of his doings in the previous life, he has gained new powers."
—Shin Megami Tensei III: Nocturne Compendium
Before the Conception, Sakahagi's previous life was that of a successful businessman. Though he seemed to be living the ideal life everyone strives to obtain, his fortune eventually collapsed and he became consumed with thoughts of killing, accusing a boy who may have been the cause of his downfall. His was one of the strong emotions that lingered and lent itself to the earth after Tokyo transforms into the Vortex World, and his desired persona emerged, taking the form of a Manikin that has nothing in mind but a thirst for power and blood.
Sakahagi first appears in one of the western buildings in Asakusa, hunting down his own kind to collect more skins and Magatsuhi. He was among those who were freed from Kabukicho Prison, and has since developed a firm resolve to no longer become subservient, going on a solitary quest to increase his powers to ultimately become the king of demons. Futomimi's visions of a peaceful world meant nothing to him. As such, he is both shunned and feared by his fellow Manikins.
Sakahagi has no qualms about murdering fellow Manikins, taking their skins and adding them to his clothes as trophies. He seems to understand that Magatsuhi is the source of a demon's power, and since Manikins are human simulacra that contain the collective emotions of numerous spirits that sought a tangible form, they are potentially an abundant source of such energy which will make his ambitions concrete.
Later on, Sakahagi had wrested possession of the Yahirono Himorogi from the fairies at Yoyogi Park construction site, putting them under a spell and turning them into wild territorial demons that keep trespassers away while he seeks out the Magatsuhi stored there. Even with all the power of Yahirono Himorogi, Sakahagi and his demon Girimehkala were both slain by the Demi-fiend.
Sakahagi is to be later reborn, called back into the Vortex World by the Afterlife Bell. His imprisoned spirit as his past self can be liberated from the Maze of Hell in the fourth Kalpa of the Labyrinth of Amala. He will gain new powers and will become part of the Foul clan, able to be summoned in the Cathedral of Shadows as the Demi-fiend's minion.