Square Enix’s Big Gangan magazine released the final chapter of the Gakuen Sensuikan-tai: Mermaid Girls (学園潜水艦隊マーメイドガールズ ) manga by Fukami Mokoto and Tokiya Seigo in its May 2026 issue, released on April 24th, 2026. The manga’s fourth and final tankoubon volume will be released on June 25th, 2026.
Writer Fukami and artist Tokiya started the manga in April 2024 in Square Enix’s Big Gangan magazine, and Square Enix published the manga’s first volume in January 2025 and the third volume in November 2025.
The manga is set in a world where extra-terrestrial life forms known as Trench Walkers have emerged from the Antarctic and are walking on the sea floor. Their goal is to reform the Earth to their liking, which involves raising the sea level by 70 meters, thus rendering Tokyo and many other population centres uninhabitable. They have also begun to change Earth’s surface water into what they call Nectar, the “divine water.”
Those who are incompatible with Nectar have a high chance of death. However, there are girls who are found to be compatible with Nectar, and they are recruited to be marines in a fight against the Trench Walkers, boarding ships to do battle in a new deep-sea front line. Hiro Todoroki, having received a message from her deceased sister, searches for the strongest Marine, Kiriri Kakuba, and, despite her doubts, decides to join the Masakado Girls’ Academy Submarine Fleet.
