Monster Musume x Overlord Crossover
Monster musume world MC is a king from the monsters world that came to the human world so he is exempt from the rules
Harem includes the MON members and main girls, add more if you know any.
Overlord comes in as a VRMMORPG and will have the MC going in and will eventually bring the girls from there to IRL the harem there is huge since there's so many girls so comment some names from there!