Kami nomi zo Shiru Sekai

Keima is a dating sim champion. Cute girls are rendered powerless by his irresistible game playing techniques. Too bad things aren't that way in the real world. That is, until his tempting game playing causes a real live—and very bubbly-cute—demon hunter named Elsie to materialize! Now Elsie wants Keima to help her free hot girls from sneaky demons who secretly possess them.
(Source: Sentai Filmworks)