A dreamlike world where science has solved everything──. The cheerful 14-year-old girl Ichiseki Akane lives a warm yet poor daily life with her reliable younger sister Momo, who takes care of all the household chores, and her troubled grandfather Kenjiro, a genius inventor who continues to strain their finances with his inventions. On clear days, they can see the artificial island Blue Island across the sea. At the center of that island stands the groundbreaking invention, the Shigen Engine, which has solved the world's energy problems all at once. It represents the peaceful future everyone has dreamed of—a happy life where everyone can smile──. However, the world is suddenly struck by a crisis. The mysterious enemy Alone appears, targeting the Shigen Engine. In a desperate situation where no weapon works, a girl clad in a powerful red suit known as the 'Palette Suit' rises to the challenge──.