Batsukoi 

The manga centers on Kahori Mirumachi, a lawyer who only gets into shallow relationships, saying that she only wants to "indulge in the delicious parts of a relationship," her only rule being to not become a part of an affair. However, despite her best efforts, she ends up falling in love with the teacher Teruyoshi Sunagoya, unaware that he is going through divorce proceedings, and thus she unwittingly gets into an affair with him.