Each episode basically reveals new stories. Each story deals with different people in certain social situations.
We see the series through Nanno's eyes.
Nanno, the main character, a mysterious girl with supernatural powers, appears in a different school every episode, where she bonds with a certain person/group of people. [Those people are either bullies, egoists, rapists...]
Nano, which is on the border of a negative and a positive character, reveals every episode some lessons and teaches us about the value of life itself.