Looking for a specific Japanese movie/drama

I watched this movie/drama a few years ago, but I can't recall its name. A girl in high school meets an alien (?) who has recently arrived on Earth. I think his name was "Nova" or something similar. He acts strangely and eventually becomes friends with the girl. There isn't any romance, or at least it isn't obvious. In the end, the other aliens come for the alien on Earth and he has to return to his home. I remember this particular scene because the other aliens were very, very pale. 

That's it! Could I ask for the name of the movie/drama?

Nazo no Tenkousei