As one of the seven mermaid princesses, Lucia must travel to the human world to protect the mermaid kingdoms.

Himawari was saved by a ninja when she was little, and has wanted to be a ninja ever since. On her first day at ninja school she meets Hayato, a non-ninja teaching to pay off his debts. Interestingly, he has the same mark on his neck as the ninja who saved her.

Mina and Mizuki sisters attended a ballet class in Tokyo. One day, the sisters return home separately, but younger sister, Mizuki, is kidnapped on the way home and discovered as a corpse. On that day, Mina blames herself for returning home, leaving her sister to practice ballet staying. Her mother, Teruko, is also very upset by the news of the discovery of her body, causing deep emotional wounds. The incident was featured on a variety show, and the mother and daughter, who couldn't stand the curiosity of the world, moved to a quiet country town far from the city. Although they started a new life, Teruko is bullied by a mysterious mad woman and Mina is bullied at school. And a mysterious murder case occurs again around them.

Hyperspace Boy Wonder Seven is a fictional tokusatsu, mentioned in TV series Giant Robot Mikazuki. This single 25-minutes episode of the "Wonder Seven" was released in 2001 as bonus with the "Tekkōki Mikazuki" DVD-box.