Haraguro Onzoushi ga Ijiwaru desu

Twenty-eight-year-old Shiho tries best to look like a successful "career woman" at work every day. Shiho has no interest in Miyagi, the handsome playboy, who sits next to her and flirts with the other female employees who surround him. One day, however, when Shiho is feeling down, Miyagi gently cuddles up to her. Shiho's heart flutters involuntarily, but at that moment, Miyagi's character changes drastically! With a fierce smile, he comes at her and says, "I'll make you fall for me...!"

(Source: Berry's Bunko, translated)