Oyasumi, Nini-chan.

In so much anguish that he couldn't sleep, Uta thought in desperation that it might be better to end it all. Just as he was about to cast himself off, an angel suddenly dove from the sky and collided with his head. And so began the heartwarming life of a young man named Uta and his self-proclaimed angel named Nini. (Source: Shueisha, translated)