Board Thread:Questions and Answers/@comment-2605:6000:5547:6E00:85EA:BB61:209B:705-20190814022128/@comment-46142448-20200621201934

There are three factors I see as limiters to a Bicorn's husband's harem's size.

First, the desires of the husband. The way I see it, a Bicorn would only be with a man who wanted a harem. Either the naturally-born Bicorn would use her innate succubus senses to detect men whose desires distinctly involve multiple girls, or the Unicorn is corrupted by a man sleeping around anyways. Thus, at least one girl beyond the Bicorn is guaranteed. Any further is determined by the Bicorn's perception of the man's desire - if the Bicorn encounters a girl who satisfies a desire no girl in the harem already does, she tries to add her to the harem.

Second, the perception of the husband regarding monster "wives". While terms regarding marriage are used throughout the setting material in reference to monster girls' bonds to human men, the concept is radically different from most human relationships in almost every circumstance. Depending on how the man of the harem perceives these relationships, the Bicorn may focus on a smaller, more romantic or intimate harem, or may ride about collecting monster girl sex slaves en masse for her beloved.

Third, logistic capability and constraints of physical housing space are a big, everpresent limit on harem size. Unless the harem relocates to Wonderland, Pandemonium, or the Abyss, or uses Space-Creating Magic and creates and corrupts a demon realm of their own, their home will have finite size and resources, and the size of harem will be constrained as such. Tying in with the second point, however, some Bicorns' husbands may not desire a "wifely" relationship with all of the girls in the harem, and they may live apart. This can help as well.

Ultimately, given the existence of Space-Creation Magic and demon realms, a harem's size is limited purely by desire.