Ryo decides to move in with his uncle to continue his education. Everything goes on as usual, until he meets his aunt Kasumi, when she goes about her personal business. This event leads to the fact that Ryo begins to have strong feelings for her and cannot think of anything else. Meanwhile, Kasumi's younger sister is immersed in her romantic fantasies about Ryo.

The action takes place in the distant future. Due to atmospheric pollution, it has become impossible to live on the surface of the planet. People have built cities high above the clouds, and below dwells a mysterious race of beings known as "shadows."