The story begins in a near-future Japan in the year 2080, where the birth rate has plummeted drastically. Society has responded by artificially extending adolescence to preserve youth, and traditional holidays like Christmas have faded into myth. Children hold higher social status than adults, and strict control policies govern minors, including arranged marriages from infancy and restrictions on normal activities like sleeping and using the toilet.

On December 25, during a snowy day, middle school student Kazushige Sanda experiences a sudden and mysterious event: his body seal is broken by his classmate Shiori Fuyumura. This seal had kept hidden his true identity as the descendant of Santa Claus. Upon the seal breaking, Sanda transforms into a figure resembling Santa Claus, complete with red attire and a magical aura.

Sanda soon discovers that he can switch between his normal middle school form and his Santa form. Eating jellybeans allows him to revert to his youthful self, while donning red clothing transforms him back into Santa. This duality becomes central to his identity and the unfolding mystery.

Shiori reveals to Sanda that she broke the seal because she believes he can help find her missing friend, Ono Ichie. Ichie disappeared under strange circumstances, and Shiori hopes that Sanda's Santa powers and connection to the forgotten magic of Christmas can uncover the truth behind her disappearance.

Together, Sanda and Shiori embark on a journey to investigate Ichie's disappearance. Their search leads them through a society that has largely forgotten Christmas and the legend of Santa Claus, encountering various obstacles and individuals who are either hostile or fearful of the old myths. The duo faces confrontations with authorities enforcing the strict societal controls on youth, as well as mysterious forces linked to the curse that sealed Santa Claus away.

During their investigation, Sanda learns more about the curse that sealed Santa Claus and the reasons behind society's rejection of Christmas. The curse is revealed to have a powerful and dangerous nature, which is why Santa was sealed and Christmas erased from collective memory. Sanda's awakening threatens to unravel this status quo, making him a target for those who want to maintain control and suppress the old magic.

As Sanda and Shiori delve deeper, they uncover clues that suggest Ichie's disappearance is connected to a larger conspiracy involving the government's control over children and the suppression of Christmas traditions. They discover that Ichie may have been taken because she possessed knowledge or abilities related to the curse and the magic of Christmas.

The climax of the season involves a tense confrontation where Sanda must fully embrace his Santa identity to rescue Ichie and confront the forces that seek to keep Christmas buried in legend. This includes a detailed sequence where Sanda, in his Santa form, uses his powers to fight off agents trying to capture him and Shiori. The fight is intense and strategic, with Sanda using his magical abilities and quick thinking to outmaneuver his opponents step by step.

In the final scenes, Sanda successfully rescues Ichie, breaking part of the curse's hold on the world. The act rekindles a faint but growing awareness of Christmas in society. Sanda, Shiori, and Ichie stand together, symbolizing hope for the return of the lost holiday and a challenge to the oppressive social order that has suppressed youth and joy.

The season ends with Sanda reflecting on his new role as the bearer of Christmas's legacy, aware that his journey is just beginning and that the battle to restore the magic and meaning of Christmas in this future Japan will continue.

The ending of SANDA Season 1 concludes with Kazushige Sanda fully embracing his identity as the descendant of Santa Claus, breaking the curse that sealed Santa Claus and restoring the true spirit of Christmas to society. Sanda, with the help of his classmate Shiori Fuyumura, finds the missing classmate Ono Ichie, resolving the central mystery. The season closes with a renewed hope for the future, as the social order begins to shift and the legend of Christmas is revived.

In the final episodes of SANDA Season 1, the narrative unfolds with intense focus on the resolution of the curse that has long sealed Santa Claus and the mystery surrounding Ono Ichie's disappearance.

The climax begins with Sanda Kazushige, now fully aware of his connection to the mythical Santa Claus, preparing to confront the forces maintaining the curse. The scene opens on a snowy December 25th, symbolic of Christmas, where the atmosphere is heavy with anticipation. Sanda, dressed in his red Santa form, stands resolute, his body seal finally broken by Shiori Fuyumura's earlier intervention. The red of his attire contrasts sharply with the white snow, visually emphasizing his transformation and readiness to reclaim his legacy.

Shiori, who has been a steadfast companion throughout, reveals critical information about Ono Ichie's whereabouts, which had been shrouded in mystery. The search for Ichie is not just a personal quest but a symbolic journey to restore lost innocence and hope in a society burdened by declining birth rates and rigid social controls. The narrative carefully depicts their journey through futuristic Japan, where children hold higher social status than adults, and societal norms are strict and controlling.

As they locate Ono Ichie, the scene shifts to a tense confrontation with the curse's enforcers--shadowy figures representing the societal forces that have suppressed Christmas and the spirit of giving. Sanda's Santa form, empowered by jellybeans that allow him to shift between his middle school and Santa forms, becomes a beacon of resistance. The battle is visually dynamic, with hand-drawn animation emphasizing the contrast between the cold, oppressive environment and the warm, vibrant energy Sanda brings.

The turning point arrives when Sanda, embodying the true spirit of Santa Claus, breaks the curse's seal. This act is depicted with a burst of red and white light, symbolizing the return of Christmas and the rekindling of hope. The curse's dissolution is not just a magical event but a metaphor for breaking societal constraints and restoring joy and freedom.

In the closing scenes, the social order begins to shift subtly. Children and adults start to interact more freely, and the legend of Christmas is no longer dismissed as a myth but embraced as a living tradition. Sanda and Shiori stand together, looking toward a future where the values of kindness, generosity, and hope are restored.

Regarding the fates of the main characters:

• Kazushige Sanda fully accepts his role as Santa's descendant, becoming a symbol of hope and change in the new society.
• Shiori Fuyumura remains a loyal friend and catalyst for change, her belief in Sanda and Christmas instrumental in breaking the curse.
• Ono Ichie is found safe, her return symbolizing the restoration of lost innocence and the possibility of a brighter future.

The season ends on a hopeful note, with the snow gently falling and the renewed spirit of Christmas illuminating the world around them.

The TV show SANDA, Season 1 (2025), does not have a traditional post-credit scene. Instead, it features a creditless ending sequence set to the song "Diary" by Soushi Sakiyama, which shows more relaxed, everyday moments of the protagonist Sanda and his classmates rather than a separate post-credits teaser or bonus scene.

This ending sequence serves as a calm contrast to the series' intense action and does not function as a narrative setup for a sequel or additional plot development after the credits. There is no indication from available sources of any extra scene appearing after the credits roll. The show's conclusion focuses on this creditless ending video rather than a post-credit scene.

Kazushige Sanda's transformation into Santa Claus is triggered when his body seal is broken by his classmate Shiori Fuyumura on December 25, allowing him to take on Santa's form by wearing red or revert to his middle school form by eating jellybeans.

Shiori Fuyumura attacks Kazushige Sanda because she believes he carries a curse that can help find her missing friend, Ono Ichie. She hopes that by breaking his seal and involving him, he will help locate Ono and remind society of the lost magic of Christmas.

Ono Ichie's disappearance is central to the plot as it motivates Shiori Fuyumura to seek Sanda's help. The search for Ono drives the story forward and is tied to uncovering the hidden magic of Christmas and the mystery surrounding Santa Claus in this future society.

In the near-future Japan of SANDA, children are highly treasured due to ultra-low birthrates but are strictly monitored and controlled. Christmas has faded into myth and Santa Claus is considered dangerous and sealed by a curse. This societal backdrop creates tension and influences Sanda's decision to become Santa to protect children and fight against adult control.

When Kazushige Sanda becomes Santa, he gains the ability to change his form by wearing red to become Santa or eating jellybeans to revert to his middle school self. This transformation is linked to the curse and the legacy of Santa Claus, enabling him to fight adults and protect children in the story.

The TV show SANDA, Season 1 (2025), is not specifically categorized as family-friendly. It is a shōnen anime with themes of mystery, action, and drama set in a near-future Japan with a dystopian atmosphere. The story involves middle-schooler Kazushige Sanda, who becomes entangled in dangerous situations involving curses, missing persons, and a societal conflict between children and adults.

Potentially objectionable or upsetting aspects for children or sensitive viewers include:

• Violence and physical confrontations: The protagonist is attacked by a classmate with a knife, indicating scenes of physical threat and possible blood.
• Dark themes: The series explores a dystopian future with declining birth rates, societal control, and the banning of Santa Claus, which may include mature or unsettling themes about survival and human connection.
• Mystery and suspense: The plot involves curses, disappearances, and danger, which could be intense or frightening for younger or sensitive viewers.
• Emotional tension: Characters face loss, fear, and conflict, which may be emotionally heavy.

There is no indication of explicit sexual content or strong language in the available information, but the presence of violence and dark thematic elements suggests parental discretion is advised for younger children or sensitive audiences. The show is best suited for teens and older viewers familiar with shōnen anime conventions.