Akuma ni Kusuri - Another Flavor

Miyamoto Momoko is a college girl working part time at a coffee shop. The majority of her customers are normal people, but she has this one regular, Sakasaki Shu, who is so much of a bad boy that he seems almost evil sometimes. Momoko becomes emotionally invested with Shu as time goes on and they begin a relationship. But being his girlfriend is an emotional rollercoaster for Momoko.

(Souce: MU)