Toshiue Shachou wa Tennen Dekiai Monster: Kousai 0-Nichi, Shojo wo Tsumareta Asa ni Propose!?

They're alone in the hotel room, and all she can do is ask him to be gentle... Shiho's trying to make ends meet as an administrative assistant at a hospitality company. Growing up in an adoptive family with a little sister, Mayu, who bullies her to this day, Shiho's hesitant about seeking love or happiness. Nevertheless, when Mayu forces her to attend a group blind date with a bunch of older men, Shiho meets Yukito, a charming man 12 years her senior. After hitting it off over drinks, they end up spending a passionate night together where Shiho experiences a man's touch for the first time. The morning after, she's thrown for a loop when Yukito proposes to her out of nowhere. However, that's nothing compared to the shock that awaits her when she finds out what he does for a living! (Source: MangaPlaza)