Shinji,
Something else that this reminded me of, the game company Atlus. They have an RPG, Thousand Arms, that uses a dating theme for one of the game aspects.
What I mean is, your character in Thousand Arms needs to get more and more intimate with a girl, so he can forge stronger weapons for him and his adventurers. So, to get more intimate with the girls of the game, you can take them on dates, give them gifts, or try their little game. It’s not a very deep dating sim, but it is one of the few English games that has it.
Just something that occured to me.
Oh, I think GameFAQ should also have a review of Graduation II. It might not be as detailed as Rowena’s, but it might give you some additional information.
Mike