From StarryHeaven:
On her sixteenth birthday, the unlucky, unmotivated and good-for-nothing Odagiri Yume saves the high-classed and lovely Momo, who claims to be the Devil. Yume confesses her wish to become special and Momo grants it: she makes Yume the representative of the earth! From now on her sixteenth birthday until her eighteenth, Yume has to give Momo seven good reasons as to why the earth shouldn’t be destroyed. The countdown for the destruction of the world has begun and only Yume can stop it.