With Japan along with most countries having developed as a maritime nation due to natural disasters, it became necessary to have specialized schools to teach skills essential to protecting the sea. The setting is one such Navy Warship High-school. The girls who enroll here study to become "Blue Mermaids" through classroom instruction and teaching of practical skills.

a group of students take a private bus owned by the school to the school building/university which is next to a port with WW2 IJN/Imperial Japanese Navy Warships, or other WW2 Navy ships from different countries