I know Harem genre list.has a
- A harem must have at least three boys and/or girls that are attracted to the focused male or female, at least three of which having a major or supporting role within their title.
Is this a Zombie? - You have Shimomura, Orito, King of Night (though, he died later on) I'm not sure about this show since there are no new guys taking King of Night's place.
- To Love-Ru - You have Zastin, that loser guy that is voiced by Bossun's VA, and your main character.
Alice in the Country of Hearts would have count, but it has 2 girls since Alice's sister is dead or missing. Don't count that franchise.
- Sword Art Online isn't a harem, but it's somewhat is. You got Klein, Kirito, and Egil for the first requirement.
- Rosario Vampire actually has a lot of guys. Gin and the Martial Arts Dude are the supporting character.