Reg is a central character in Made in Abyss: Mezameru Shinpi, the film that continues the narrative of the original series. He is a robotic boy of mysterious origin, discovered by the protagonist Riko in the depths of the Abyss. Reg retains no memory of his past before meeting Riko, including his purpose, his creators, or why he possesses such extraordinary physical capabilities. His appearance is that of a young human child, but his body is composed of advanced, unknown materials, with a distinctive helmet-like headpiece that covers the top of his skull and long, dark hair that falls past his shoulders. His body is warm to the touch, and he can eat and sleep, but he does not age or require sustenance in the same way a human does.

Reg’s personality is defined by a gentle, earnest, and deeply protective nature. He is kind-hearted, often displaying a childlike curiosity about the world around him, yet he also shows remarkable maturity and composure in life-threatening situations. He speaks in a polite and somewhat formal manner, reflecting an inherent sense of duty and honor. Despite his mechanical body, he exhibits a full range of human emotions, including fear, sadness, joy, and anger, often becoming flustered or embarrassed by Riko’s more forward or reckless behavior. He is fiercely loyal and feels a strong sense of responsibility toward Riko, viewing his primary purpose as ensuring her safety during their descent into the Abyss. This protectiveness sometimes borders on overbearing, but it stems from genuine care rather than condescension.

His primary motivation throughout the film is twofold: to help Riko reach the bottom of the Abyss in search of her mother, and to uncover the truth of his own forgotten identity. He believes that the answers to his past lie at the Netherworld’s deepest point, and this shared goal binds his fate to Riko’s. Unlike many delvers who are driven by ambition or greed, Reg’s journey is propelled by loyalty and a personal quest for self-discovery. He does not seek treasure or fame; rather, he seeks meaning and a place where he belongs. His role in the story is that of both guardian and companion. He provides the physical strength and combat capability that Riko lacks, while she provides the knowledge, mapping skills, and delver instincts that he does not possess. Together, they form a complementary pair, with Reg acting as the shield and sword against the Abyss’s many deadly creatures and environmental hazards.

Key to Reg’s character is his relationship with Riko. Their bond is the emotional anchor of the film. He trusts her judgment implicitly, even when her decisions are perilous, and he constantly monitors her health and stamina, as the Ascension Curse of the Abyss affects her human body far more severely than his robotic frame. He is also shaped by his memories of a mysterious white whistle delver from his past, a figure who appears in fragmented recollections and whom he calls by a name he cannot fully recall. This figure haunts his dreams and fuels his desperation to remember, creating an internal conflict between his present duties and his elusive past. Throughout Mezameru Shinpi, Reg faces trials that test his emotional endurance, particularly when he must confront the limits of his own power and the moral weight of using his abilities against living beings. He struggles with the fact that he was built as a weapon, and he grapples with the fear that his original purpose might be destructive or antithetical to the bond he has formed with Riko.

Reg’s development in this film is subtle but significant. He transitions from a mostly reactive guardian to a more proactive partner, making difficult decisions that affect their survival. He learns to manage his impulsiveness, particularly when his protective instincts clash with Riko’s own determination to face danger head-on. He also begins to accept his dual nature as both a machine and a person, recognizing that his memories, even if incomplete, do not solely define him. His growing emotional complexity is highlighted in moments of vulnerability, where he questions whether he is truly deserving of Riko’s trust or whether his hidden past will ultimately betray her.

In terms of abilities, Reg possesses several extraordinary traits that make him indispensable in the Abyss. His most prominent power is the Incinerator, a devastating energy beam that fires from the palm of his hand. This weapon is immensely powerful, capable of annihilating large creatures and even altering the landscape, but it comes with a severe cost: each use drains his energy to the point of unconsciousness and leaves him vulnerable for an extended period. He also has extensible arms that can stretch to great lengths, allowing him to reach distant objects, grapple onto ledges, or pull himself and Riko across chasms. His body is incredibly durable, resistant to blunt force, high temperatures, and the corrosive effects of the Abyss’s environment. He possesses superhuman strength and agility, enabling him to leap vast distances and carry Riko with ease. Additionally, his senses are sharper than a human’s, allowing him to detect threats from afar. However, he is not invincible; his mechanical components can be damaged, and he experiences pain, albeit differently from a human. He also suffers from the same Curse of the Abyss as any living being when ascending, though the effects are less severe due to his non-biological nature. His most mysterious ability is his apparent connection to the ancient relics of the Abyss, as he can instinctively interact with certain artifacts that baffle other delvers. These powers, combined with his unwavering loyalty and growing self-awareness, establish Reg as a poignant figure caught between two worlds—the human emotions he feels and the inhuman origins he seeks to understand.