A volume of short sci-fi shoujo stories all featuring a new race of humans called Unicorns. The major theme in all of the stories are about human emotions. As the characters in the story try to interact and relate to these Unicorns who lack a lot of the natural emotions humans normally feel.

The story A, A' raises a troubling question: how would you feel if your lover died—and was replaced by a clone? Could you recreate your relationship with someone who was physically exactly the same but didn't share any memories of your life together?

In 4/4, teenaged Mori flunks out of an ESP training program. But when he meets Trill, a beautiful Unicorn, his latent abilities begin to blossom...

In X+Y, Hagio uses science fiction to explore questions of gender and sexual identity. Time has passed, and once again, Mori finds himself inexorably attracted to a member of the unicorn race - but this unicorn is male... and so is Mori.