Tanaka-san with the Pudding is a Beast.

Chihiro is an OL who's not good at remembering names. Suddenly she was forced to change departments and was in a pinch! Even if she could remember names, everyone is indistinguishable because of their suits! Meanwhile, a male employee always gives her her favorite pudding. Chihiro nicknamed him Pudding Tanaka, and they became close friends. Throughout that, he was always a gentleman, but something changed... Source: MU