Living by the sea, protecting the sea, and journeying across the sea, that is the life of the Blue Mermaid, group of women trained to operate navy warships to protect international peace and handling maritime disaster. 15 year old girl, Misaki Akeno aspire to become one of the Blue Mermaid. And so, she attended Yokosuka girls High school where she became the captain of the Harekaze with her classmates as her crew. Unfortunately, on their first day of school, they got attacked by their instructor's ship which forces them to defend themselves. In result, they are now hunted by authorities for mutiny. However, things are getting more complicated when many of their schools' ships also mutinied which is up to Misaki and her crew to get to the bottom of this incident while being on the run in this nautical adventure.
