Wasn't the number 8 (days in a week) already stated as the maximum number of people for a socially acceptable harem? Anyone who has watched anime for more than a few months would know such numbers aren't thrown in the air for laughs only. I can't help but think the princess merchant will claim one of the slots. From a technical perspective she has had too many scenes to be a throwaway character, but also story wise she could be used to heal the relations of the two countries. A political marriage, that is.