Purin no Tanaka-san wa Kedamono.

Chihiro, an office worker who absolutely hates remembering people's names, is transferred to a new department, and things take a turn for the worse! All her new colleagues are neat and tidy in suits, making it impossible to tell them apart... But then, a male colleague appears, offering her her favorite pudding as a helping hand! Chihiro calls him "Pudding Tanaka," and they become close friends. But then, one day, this usually gentlemanly man suddenly transforms—!?

(Source: Alpha Polis, translated)