Ever since I played this I tried to find something like that but without this constant humiliation and coldness to the MC by just every NPC except the lewd elf. The only game that I managed to find is
NTR Tales - Adventurer Corruption, but it's still in the cooking. The dev doesn't have a good track record, but surprisingly this one might come out good once finished (they promise to release it in October). It has the same premise - you can ask the experienced adventurer to help clearing the dungeon, but each time you kill the boss the gf will fuck him as a token of gratitude. Whilst out of the dungeon, she wonders around the city, getting harassed by random NPCs corrupting her in the process. So - really similar to this game, but less nasty to the MC.