This argument every time. Having an optional harem for me is the same as having optional NTR in a game and your girl can cheat on you when you pick certain choices. I don't want a girl that is capable of cheating on me period, not just when I make the right choices for that not to happen. In the same sense I don't want a girl that is capable of sharing me if I make certain choices, I want a girl that wants me all to herself, and the most sad part about harem is that it means that EVERY girl can be part of a harem, because that is the definition of the harem, for me to actually have an option to romance I need atleast 1 girl that is not going to be ok with being a part of a harem, if there were like 10 girls and 9 of them would be ok with sharing the MC and just 1 would not be ok I would go for that 1 and be happy, but harem always includes ALL, so it leaves me with no desirable romance option, not a single one. This is just my humble opinion - a girl that is ok with sharing me is cuckqueen that is not worth pursuing, I don't feel loved unless a girl wants me all to herself.
Other than that there are 48929473823 harem games out there, games in which you can be in a monogamous relationship that ends when you cheat are like needles in a stack of hay.
Though:
Apparently there won't be a consensual harem, there will just be a cheating MC who keeps his cheating secret. That is ok, so long as girls brake it off hard when they find out.