"Soreike! Anpanman Minami no Umi o Sukue!" is a feature-length anime film based on the popular "Anpanman" franchise, created by Takashi Yanase. The story centers on Anpanman, a superhero made of anpan (a sweet bread filled with red bean paste), and his friends as they embark on a rescue mission in the southern seas. The narrative begins when Baikinman, the series' recurring antagonist, creates a powerful new weapon called the "Baikin Bazooka," which he uses to cause chaos. During one of his attacks, Baikinman accidentally damages a ship carrying a group of children, causing them to drift into the dangerous waters of the southern sea.

Anpanman and his friends, including Shokupanman, Currypanman, and Melonpanna, set out to rescue the children. Along the way, they encounter various challenges, including treacherous weather, sea monsters, and Baikinman's relentless interference. The group also meets new allies, such as a kind-hearted mermaid named Pearl, who aids them in their journey. Pearl's knowledge of the southern seas proves invaluable as she guides the team through perilous waters and helps them navigate the mysterious underwater world.

As the story progresses, the stakes rise when Baikinman allies with a powerful sea creature to further his plans. Anpanman and his friends must work together, using their unique abilities and teamwork, to overcome these obstacles and save the children. The film emphasizes themes of courage, friendship, and perseverance, as the characters face both external threats and internal doubts. The climax involves a dramatic confrontation with Baikinman and his sea creature ally, culminating in a resolution that highlights the importance of kindness and cooperation.

The film maintains the lighthearted and educational tone characteristic of the "Anpanman" series, while introducing new elements of adventure and danger. It features a mix of action, humor, and heartfelt moments, appealing to both children and longtime fans of the franchise. The characters' distinct personalities and abilities are showcased throughout the story, reinforcing their roles as beloved figures in Japanese children's media.