Don’t you think selling aphrodisiacs publicly could lead to trouble? Especially since you have a harem, and your girls are vulnerable to its effects? What if someone turned that against them? Just thinking about that freaks me out

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They are not mind controlling drugs dude. Yeah they make you horny but a lot of things do, that's like saying that if a dude goes to see a movie with a female friend and then during the movie a hot sex scene is shown then he is going to cheat his gilfriend with his friend because he got horny. If the dude is no asshole he would just go to his girlfriend, same with the aphrodisiacs.
In fact the aphrodisiacs are even more difficult to work out than a horny movie, you have to spread it in the skin like applying a cream or an oil massage, so the guy would have to find a way to convince a girl with a boyfriend to let then spread a strange cream on their bodies. Sure there are ways that someone can actually pull this off but if the MC tells the girls about the aphrodisiacs after he starts selling them then they can be aware and be cautious, and even if someone pulls it off if they are aware that they may have been dosed with the aphrodisiac then they can just run to the MC.
If this was a drink type substance that you could slip in someone's drink then I would be worried too, but with what it is I think that common sleeping pills are more worrisome than this recreational drug.
And sure, melena fell for it but lets look at how it happened. She let leo put the cream on her since she though it was sunscream, she was unaware of the aphrodisiac and it's effects, and she is the type of girl that jumps from boy to boy and is not in any kind of relationship. Also she was left alone with leo in a beach with no one else she knew (since the MC and steph were having their fun), so yeah. there are ways to pull it off but I think normal drugs are just easier to use in any kind of case.
If your girl goes to the beach with a guy without telling you or taking you with her, and lets that guy put sunscreen on her, your relationship is already in a bad place.