@GerryCerryBerry
True, but it's still odd to see isekai where the mc tries to sell or gain fame through something they should already have. In this case, it's clear the author knows they would have soap and has the mc sell it's quality to them. That's a big improvement but it's still kinda wrong. We actually have a kinda hygiene culture built up through advertising over the last century that has made us believe certain things are necessary (such as mouthwash which was just floor cleaner they convinced people to put in their mouths by calling having bad breath a disease called 'halitosis' and running ads saying everyone was laughing at you behind your back about it) or that they are necessary in excessive amounts (such as washing your skin daily with soap which is bad for it). So it would be weird for them to get much traction without doing the same kind of advertising that was done back in the day.
Well, again, this is better as the mc isn't trying to appeal to people based solely on the fact he has soap. He's appealing through it's quality to someone who would have a specific interest in it, his own charm in the conversation, and repelling this attack with his own power and protecting those he's appealing too. It's a much more realistic, believable plan where no one's reaction to anything is absurd.