Ryûji Morisaki is a widower, profoundly devastated by the accidental death of his wife, Lisa Morisaki, ten years prior. Lisa suffered a chronic illness that often left her bedridden; she died in a fall while Ryûji was away on a mission. Her loss initiated his prolonged quest to resurrect her, despite her earlier request that he promise to live happily after she was gone—a promise his grief prevented him from fulfilling. He serves as a substitute teacher for Asuna Watase's class, demonstrating extensive knowledge of Agartha, a legendary underground realm associated with the dead. This knowledge directly fuels his personal mission. Secretly, he commands the paramilitary group Arch Angels, orchestrating operations to locate and infiltrate Agartha. His singular objective is to reach Agartha's Gate of Life and Death and use its power to resurrect Lisa. During the expedition into Agartha, he initially presents himself as protective to Asuna, though his actions are primarily driven by his own goals. He later reveals his identity as commander of the Arch Angels after they secure entry. Throughout the journey, he exhibits ruthless determination, employing force and manipulation to overcome obstacles, including confrontations with Agarthan guardians like the Quetzalcoatl and the Izoku. His obsession strains his relationship with Shin, Shun's younger brother, who opposes Ryûji's plans for disrupting Agartha's natural order. At the Gate of Life and Death, Ryûji proceeds with the resurrection ritual despite knowing its severe costs. The process demands a physical sacrifice, costing him his right eye, and requires a living vessel for Lisa's soul, inadvertently leading to Asuna's possession. When Shin destroys the Clavis crystal to stop the ritual and free Asuna, Ryûji is left emotionally shattered. Lisa's spirit, speaking through Asuna, urges him to find happiness without her. In despair, he requests death from Shin, who refuses, stating that carrying loss is a human curse Ryûji must endure. Following these events, Ryûji chooses to remain in Agartha, separating from Asuna and Shin as they return to the surface. This decision signifies a form of acceptance, albeit unresolved, of his grief and Lisa's permanent absence. His arc illustrates a transition from relentless, self-destructive obsession toward a fragile acknowledgment of loss; his ultimate future in Agartha is not detailed.