I don't know anything about DxD (I'm guessing it's an anime or manga), so I don't know the names or have any point of reference for that. But I like the banner image and the game says it's a harem. But I read the thread and I am a bit confused, after seeing this:
Since I don't know the story from DxD idk if "Sirzechs Lucifer, Zeoticus Gremory" is one person, two people, something else... And I'm not sure what "NTR type that are popular," means, is that like Netori, since this quote seems to rule out the other types:
So, from what I think it means, it seems like in DxD there is a main character (Issei?) that has or gets a "harem," but in this you play as someone else who will steal his harem? Now, since I don't know DxD and the type of story it is, are the girls all already having sex with this Issei guy, thus the Mc of this is just stealing away his sloppy-seconds? Or is like an "alternate version," where the Mc in this prevents Issei from getting any girls in the first place? Or is DxD one of this "harem" anime where the Mc never does anything with the girls who are all obsessed with him anyway and so them being Issei's "harem," doesn't actually mean much other than that this Mc is making them want him and not the other guy kind of thing?