Isekai Trip-saki de Tasukete Kureta no wa, Hitogoroshi no Shounen deshita.

Synopsis

One day Megumi got transported to another world. She swiftly found herself assaulted by bandits, but a young man came to her rescue. She quickly became infatuated with him, and the two started a sexual relationship. She doesn't know anything about this world, and nobody explained the rules to her... But she believes that her savior will protect her. But what does he want? He seems to be after something he seems to be using her to make something happen... However, Megumi has no idea. And that's how her new life begins. (Source: MyAnimeList)