I always thought the normal version of the game was supposed to be dark, is the dark version that much darker? (I havent played the original by the way, though seeing the tags I thought it was still dark).
I don't think the original game is dark at all. I wouldn't know which tags gave you the impression that it is. The "rape" tag is there for one scene most players will miss (because it includes a decision hardly any player will make without a walkthrough in my guesses) which isn't especially graphic and does not include MC or any of his LIs.
There is a bit of darkness (okay, some) in the family backstory of one of the girls, but that gets resolved pretty quickly.
If you consider the "Corruption" tag as indicative of possible darkness and secret manipulation, well, I wouldn't even know what that is doing here. There's not really much corrupting going on since basically everybody is a pervert from day one to some degree.
I agree that this game is mostly light hearted, with silly jokes, silly karaoke (you will miss out on some fun if you don't know some of the greater hits of the last century). The discussion above about how much of a bumbling oaf really is versus playing it should also give a hint that it is not entirely serious.
If you have any particular tags you fear, share them with us (after all, sharing is a tag for this game - well, swinging, close enough) so we can put your worries about it to rest.