Shūji Nakaumi, a middle school student from Nakano Ward, was selected as a God candidate by the angel Ogaro. Ogaro granted him Wings for flight and a Red Arrow compelling anyone struck to fall in love with him for 33 days. Orphaned after the rapid deaths of his grandfather, parents, and three classmates, Nakaumi had secretly facilitated these deaths using the Red Arrow, believing he fulfilled genuine desires to die. He tested it on his suffering, life-supported grandfather, who then removed his ventilator and died peacefully; Nakaumi perceived this as mercy. He later shot his despondent father after his mother left, compelling suicide. When he shot his remorseful mother, her partner survived, leading Nakaumi to conclude the arrow revealed true intentions, distinguishing sincere suicidal wishes from attention-seeking.

Nakaumi maintained a stoic, expressionless demeanor. He had a slim build, rounded face, dark circles under his eyes, and thin black hair often covering part of his face. Outdoors, he wore plain shirts, gray sweatpants, and dirty sneakers, preferring bare feet indoors. His philosophy centered on euthanasia and the right to die, asserting those wishing to end their lives deserved assistance if lacking courage. He initially saw the Red Arrow as a tool of hope for dignified deaths. However, after Mirai Kakehashi condemned assisted suicide as criminal, Nakaumi resolved to stop but planned one final act: helping his brother Hirokazu die before his own suicide. He criticized those preventing suicide without addressing despair. A conversation with Mizukiyo Minamikawa, who argued suicide inflicted lasting trauma citing grief over Kanade Uryū, persuaded him to abandon his plan for Hirokazu and seek a suicide burdening no one.

During the God selection, Nakaumi aligned with Mirai and others against Kanade Uryū (Metropoliman). When candidates declared their goals, Nakaumi advocated for societal acceptance of suicide. He later shifted allegiance to Professor Gaku Yoneda after learning Yoneda's theories about God and the selection. Yoneda exploited Nakaumi's aversion to burdening others, manipulating him with a Red Arrow to ensure loyalty. Under Yoneda's direction, Nakaumi participated in timed killings using White Arrows and took hostages, including Saki Hanakago. Yet, even under the Red Arrow's influence, he could not kill Saki when she expressed a will to live.

Following Yoneda's defeat, Nakaumi volunteered to become God, receiving unanimous agreement. As God, he fused with the previous deity and erased global memories of the selection process, though candidates could choose to retain theirs, then ascended to Heaven. Over six years, observing human suffering, Nakaumi grew overwhelmed by guilt over his past actions promoting suicide. Ultimately, he committed suicide while the angels were distracted. This act triggered the destruction of Heaven, erased all human existence, and caused Earth's deterioration.