Shigoto Ningen na Hakushaku Reijou wa Koori no Saishou-sama no Ai wo mi Ayamatteiru

Despite being a countess's daughter, Olivia is completely devoted to her work. As the assistant to Arthur, a workaholic feared as the "Ice Prime Minister," she handles an extraordinary workload day and night. Although she harbors feelings for Arthur, she suppresses them, believing their love is unworthy. But then, he suddenly proposes to her! And, for the sake of her work (?), she accepts without hesitation...!?

(Source: Overlap, translated)