I'm surprised that there wasn't a thread this already.

The World God Only Knows(Kami no Mizo Shiru Sekai)

Quote Originally Posted by MangaShare
Katsuragi Keima is known on the net as the god of getting the girls
while in real life he’s known as otamegane and he hates all real girls.
However he is approached by Erushii, a devil from hell, to help her in
catching runaway spirits that hide in people. Apparently the spirits
only hide in the hearts of girls and the only way to get the souls out
is by making the girl fall in love so the spirit gets forced out. And
he’s not allowed to fail or he will lose his head.
View it here