Isekai Goumon Hime

Isekai Goumon Hime summary:

After dying, Sena Kaito was reborn in another world and confronted with a peerless beauty, Elisabeth, who had appeared before his eyes. Introducing herself as "Torturchen," she commanded Kaito to become her servant, but he refused on the spot. When Elisabeth presented Kaito with the choice of either torture or butler, he immediately submitted and began to serve at Elisabeth's side, to accompany her until she completed her mission.