"Himitsu no Akko-chan: Umi da! Obake da!! Natsu Matsuri" is a feature-length anime film based on the classic magical girl series "Himitsu no Akko-chan." The story centers on Atsuko "Akko" Kagami, a young girl who possesses a magical mirror that allows her to transform into anything she desires. The narrative unfolds during a summer festival, where Akko and her friends embark on an adventure filled with mystery, supernatural elements, and lighthearted humor. The plot begins with Akko and her classmates preparing for a summer festival near the seaside. Excitement builds as they plan to enjoy traditional festival activities, but their plans take an unexpected turn when strange occurrences begin to happen. Rumors of ghosts and supernatural phenomena spread, creating an atmosphere of intrigue and suspense. Akko, ever curious and brave, decides to investigate these mysterious events using her magical mirror. Along the way, she encounters a variety of whimsical and eerie characters, including mischievous spirits and otherworldly beings. As the story progresses, Akko's transformations play a key role in solving the mysteries and helping those in need. Her magical abilities are tested as she navigates challenges that blend the ordinary with the fantastical. The film maintains a balance between light-hearted moments and moments of tension, capturing the essence of a summer adventure. The seaside setting and festival backdrop provide a vibrant and nostalgic atmosphere, enhancing the story's charm. The main characters include Akko, her best friends Moko and Kko-chan, and her rival, the mischievous boy Goro. Each character contributes to the narrative through their unique personalities and interactions, adding depth to the story. The film explores themes of friendship, courage, and the joy of discovery, staying true to the spirit of the original series. The blend of magical elements, humor, and a touch of mystery makes "Himitsu no Akko-chan: Umi da! Obake da!! Natsu Matsuri" an engaging and family-friendly anime film.