@Fushiginiku I don't remember other isekai titles with the Soap trope. Although I do recall Shampoo as a recurring trope. True soap was only widespread in China in the modern age, detergents were not as popular as ointment and creams. It's likely became a storytelling shorthand to signal...
@Fushiginiku this a parallel world, it only looks like the Middle Ages. Neither Babylon nor England exist there. Initially soap was just used for washing objects, it was during the civil war when body washing with soap was a practice. It was only a century ago when medicine adopted the practice...
@Fushiginiku Ancient Babylon don't have magic and elves, soap is not universal. In many ways Ancient people were more advanced than medieval people, it was called the dark ages because past knowledge were forgotten and little to no progress happened at the time.
@WillTell religious people think they can bargain with their gods. Throughout history they have performed atrocities such as human sacrifices, slavery and genocide.