Tensei Shitara Maou-Sama Ni Dekiai Saremashita

Haruka, an employee for a real estate company, is lamenting about her mistakes at work as well as her unrequited love with a senpai who recently got married when a "meteor" suddenly hits her window. The suspicious man who fell from the sky is the self-proclaimed demon king?! He then proceeds to tell her that in her previous life she was the saint, which makes him her archenemy... like hell anyone would believe something that sounds as if it came from a light novel! Then he declares, "I'll make you happy, and when you've regained hope I'll plummet you into despair!" Corporate slave who was a saint in her past life x demon king, the story of their cohabitation as the demon king becomes a doting lover. (Source: Mangaupdates)