Yandere Ouji no Nigegoshi Cinderella

The plain office lady Suzu has fallen into a one-sided love with the kinder than anyone, super-handsome Chief Serizawa. Popular among the female staff, he’s nicknamed Prince Serizawa. Though she had decided to mind her own social position by ending it with just longing, one day during overtime she witnesses Serizawa’s outrageous behavior. Source: NU