And just in case you anyone thinks that I was being awkward, I've seen many different interpretations of harem being used, e.g. people asking me about a Monica, Jenna, Katie harem. Or a Katie, Debbie, Lily harem....
So, in the context of a FULL Harem where MC ends up in an open relationship with ALL females and all of them know about each other and willingly share....Then I do not foresee that happening! It just wouldn't make sense even in the non-realistic world of WTHI.
However, that's as far as "canon" goes. I did mention in the past that I would consider adding in a "Complete fantasy" epilogue for those that would like to end on a harem note. It won't have a natural progression from the normal ending(s). After the game ends, this Harem alternate ending would need to come with a silly reality jump / disclaimer lead-in like "Eventually, all parties forgive MC and/or each other and end up accepting his philandering ways, etc... and they all live happily ever after...." and then some imagery to back it up. There won't be a natural (stats/decisions/dialog) way to smoothly transition to this ending (if we even decide to add it). Hopefully that makes sense? (He says as he slips on his coat and sneakily edges towards the back door...)