The story of Idol Memories is set in the near future, where live idol music performances in virtual reality have become commonplace. Against this backdrop, a pair of rival idol groups compete for the coveted "tiara," which represents the number one spot in the "Idol League."

Long, long ago, there existed a world of magic and science. God, afraid of man's potential, split the world in to the world of science, Elde, and the world of magic, Fandavale. One day in Fandavale, a terrible witch named Cendrillon (Cinderella) revives. Cendrillon plots to rule both worlds, and searches for the "key" which holds tremendous power. A young boy from Elde by the name of Sōta meets a mysterious girl from Fandavale, Akazukin, and her talking wolf companion, Val. Sōta learns that he is the key Cendrillon is searching for. Now it is up to Akazukin, Val, and the other Fairy Musketeers to protect Sōta from Cendrillon and her Nightmarelians who wish to obtain the power he mysteriously possesses.

Kouichi Uehara is a fourth grade student living in the suburb of Tokyo. One day, he picks up a large stone which turns out to be a fossil of a baby "Kappa" who has been sleeping underground for the past 300 years, and names it "Coo." They become good friends and Coo starts living with Kouichi's family. However, Coo has a hard time adjusting to life among humans and misses his kind.

Princess Sapphire is a girl raised as a Prince. Through the mischief of an angel, the princess is born with both a girl's body and boy's mind. Since there is no boy successor in her kingdom, Sapphire is raised as a boy, but evil ministers try to reveal her secret. Unable to put up with the kind of vicious conduct prevailing in the kingdom, Sapphire disguises herself as "Princess Knight" and wields her sword of justice. This is an animated version of the girls' manga featuring Sapphire's romance and adventure, which marked the first made-for-TV animated program geared towards girls in Japan. (Source: Official site)