Manga Ridge Harripersad of
CGMagazine noted the manga's narrative depth, observing that it contained strange stories from Itagaki. He described the artwork as distinct from her previous series,
Beastars, and highlighted her distinctive interpretation of
Santa Claus. Although he initially found the protagonist stereotypical, Harripersad later considered the characterization appealing, drawing a parallel to Okarun from
Dandadan. Bolts from
Anime News Network praised the handling of the lore and the Santa character, but criticized Sanda's tendency to overanalyze situations and Fuyumura for occasionally mistreating him despite her reliance on Santa's power. Raquel Ramia of
Akibahara Station commended the narrative for its themes of children leaving childhood behind, which resulted in significant character development for the main cast. She speculated about the potential for a
love triangle despite its absence in early chapters, and praised the artwork for its fight scenes and detailed character expressions during dramatic moments. Reviewers at
Manga News expressed surprise at the violence in the fourth volume, particularly a subplot involving a criminal and Sanda dealing with children's deadly wishes, which one reviewer found graphically disturbing. Kō Aokage of ''
called Sanda
a unique fantasy hero story that used the premise of a child transforming into Santa to reflect on modern societal issues, such as low birth rates and excessive state control. Aokage noted that the series explores the contradiction between state protection and individual autonomy, with its "intergenerational" and "system versus individual" themes resonating strongly. By forgoing the "anthropomorphization" metaphor of Beastars'' and having characters confront the system directly, the drama was considered more realistic, suggesting a maturation of the author's perspective.
Anime Lucas DeRuyter from Anime News Network enjoyed the "ridiculous" premise and found Sanda's powers and the series' setting compelling. The animation by
Science Saru was praised for its visuals in the premiere, particularly a scene where the protagonist uses his powers against an explosion. DeRuyter, who watched the English dub, commended Ben Balmaceda for his energetic portrayal of Santa Claus. Chris Beveridge of
The Fandom Post found the initial conflict between Fuyumura and Sanda intriguing and noted the unique character designs. He considered the story over-the-top but felt the duality of Sanda and Santa was effective, expressing interest in future episodes. Isaiah Colbert of
Gizmodo enjoyed the mix of horror and comedy. He stated that the anime stood out due to Itagaki's storytelling, which reminded the reviewer of his positive experience with
Beastars, and commented that Science Saru amplified the manga's appeal. Elijah Gonzalez of
Endless Mode praised the anime's portrayal of
LGBTQ+ themes, gender, and puberty in a healthy manner. He cited the handling of Fuyumura's identity and her relationship with Ono as major examples. In an article titled
Sanda Shows that Adolescence is Supposed to be Awkward for
Anime News Network, DeRuyter noted that the series' core theme involved accepting adulthood, a process embodied by the protagonist obtaining new powers awakened by his genes. DeRuyter also noted that the protagonist was distinguished by his sympathy toward the Fuyumura during her
identity crisis, a condition society refused to acknowledge in children. As the narrative progressed, Sanda sought out other individuals troubled by social issues that adults ignored, aiding them while simultaneously improving his relationship with Fuyumura. The ANN editorial team listed the series as the best anime of Fall 2025, citing its lore and themes, as well as its production values. Steve Jones related to the characters' reflections on their growth while watching the series, as he did with his own experiences of puberty. It was also listed as the seventh best anime of 2025. Commenting on the series' thought-provoking themes, Ross Locksley from
UK Anime Network said that, while Santa is an appealing character due to his powers and personality, the anime stands out more for its large cast and focus on drama. A major example of this is Sanda's fiancée, Nico, who, rather than being a stereotypical abusive heroine, is actually devoted to her relationship with Sanda, while Fuyumura also has a notable relationship with Ono. The antagonists Namatame and Oshibu also received positive response for their portrayal of the theme of staying young. ==Notes==