"Made in Abyss: Dawn of the Deep Soul" is the third installment in the "Made in Abyss" series, serving as a direct sequel to the first season and bridging the narrative to the second season. The story continues the journey of Riko, a young Cave Raider, and her robotic companion Reg as they descend deeper into the enigmatic and perilous Abyss. Their goal is to reach the bottom of the Abyss, where Riko hopes to find her mother, Lyza, a legendary White Whistle explorer.

The film focuses on the duo's arrival at the Fifth Layer, known as the Sea of Corpses, where they encounter Bondrewd, a mysterious and morally ambiguous White Whistle known as the "Lord of Dawn." Bondrewd operates a research facility called Idofront, where he conducts experiments on humans and creatures to unlock the secrets of the Abyss. His methods are ethically questionable, often involving the exploitation of children, including Nanachi, a former test subject who now accompanies Riko and Reg.

Bondrewd's primary experiment revolves around the creation of "Cartridges," which are children transformed into tools to mitigate the Curse of the Abyss, a debilitating effect that afflicts those who ascend from its depths. His ultimate goal is to harness the Abyss's power, even at the cost of human lives. Riko, Reg, and Nanachi are drawn into a confrontation with Bondrewd, who seeks to capture Reg for his unique robotic abilities.

The narrative delves into themes of sacrifice, morality, and the consequences of unchecked ambition. Bondrewd's character is portrayed as both a brilliant scientist and a morally bankrupt figure, creating a complex antagonist. The film explores the emotional and physical toll of the Abyss on its explorers, particularly through the experiences of Nanachi, who struggles with guilt and trauma from their past under Bondrewd's care.

The climax of the story involves a tense battle between Reg and Bondrewd, showcasing the latter's formidable combat abilities and technological prowess. Despite the odds, Riko and her companions manage to overcome Bondrewd's forces, though not without significant personal cost. The film concludes with the group continuing their descent into the Sixth Layer, setting the stage for further exploration and challenges in the Abyss.

"Dawn of the Deep Soul" maintains the series' signature blend of dark fantasy, emotional depth, and world-building, expanding on the lore of the Abyss while deepening the characters' relationships and motivations. The film serves as a crucial narrative bridge, advancing the overarching story while delivering a self-contained arc that explores the darker aspects of the Abyss and its inhabitants.