just remember that the definition of a real harem involves the main girl being okay and accepting of the polygamous relations (polyamorous). head wife has always been in control and its not a harem if she isn't fine with it (also I cant stand it when people treat SAO as a harem despite asuna being first in line to clip kirigaya's balls if he even tries to set one up, nevermind the fact that he does chase or hit on every girl he encounters). A harem is only as large as the number of partners the MC can amass that ALL share the same accepting view regarding the others, and share mutual romantic interest (hence why besides emperors who used their status to please the girls, the count tends to stop at 3-4 people max)
currently re-reading TWGOK from the beginning, another series is Mahou Sensei Negima (where it is a literal class of girls, practically none of which have any real romantic interest in the main, yet the chosen girl was a bit out of left field and you only find out if you read far enough in the follow-up story UQ Holder).
the best harem is one where all members are in love with all over members ;P a small group but VERY polyamorous