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."

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.

Sorao is an ordinary student who lives an ordinary everyday life of a typical kid, accidentally makes friends with two aliens stranded here on Earth. His life changes as he decides to help them find a way to get home. When they do reach the aliens' homeworld, Sorao along with Miki, discovered a blood feud between two different tribes. Things gone awry as the tribes' representatives try to out do one another in search of the missing treasure of the past with the help of an uncovered clue. (Source: ANN)

Rinne no Lagrange short specials included in the Rinne no Lagrange Season 2 Blu-rays and DVDs.