DearS is about where an alien ship crashed landed near the bay of Japan and the government were nice to welcome the aliens, called DearS's, to live with them. A teenage boy Takeya doesn't care about the incident until one day he runs into a DearS and the story begins.
Funny, real funny and romantic. There are 7 volumes to the manga but still being translated. The anime is out. I think if you like Chobits, check DearS.