4 Years of Service
While I disagree with your assessment of the story, as I find it interesting and compelling personally and find my self wanting to see where it goes, I do agree with the vibes given by the handling of the Boxed In girls. I'll comment more below.
I agree with other's who've pointed out that this isn't NTR. That is technically correct. But I think it does give off similar vibes. The Boxed In MC is dead, but that game was built on a premise of the girls wanting him so badly that they set up an elaborate game just to get him to fuck them, taking many of their virginities and impregnating many of them. And even if you wanted to assume that the canon ending was the one where he resists (which the dev could have had as the canon ending if he wanted to use the girls) 1. It would still mean those girls had set all that up because they wanted him so badly, and 2. he still did sexual stuff with some of them even on that route because you can't avoid everything. But this game makes it clear that the canon ending if the full "harem" ending for that game because it's literally used as a joke for what got him killed. He had a heart issue and his heart couldn't take all the sex he was having.
So, even though it is true that it is technically not NTR, it still gives those vibes to a lot of people who connected with and liked the MC and family from that game and from the way the girls were in that game it feels like they wouldn't do just move on so fully just a few years later.
This is why I have suggested before (not sure if here or on another site) that BadBob might want to consider having this game take place in an alternate timeline. One where the Boxed In MC's heart defect caused him to die before the events of Boxed In could be planned or executed. This would mean that you could have the S&P MC come in after the girls had years of morning their father, but having not had him, that will have just been a crush or idea, not something they got and now moved on from. So the S&P MC isn't replacing the father he is now a new person that the girls can develop feelings for without that baggage. And, while in Boxed In, several of the girls learn the truths about their situation, such as being sister cousins, or other things, those things could still have been discovered by the girls in the interim since the Boxed In MC's death, his death being the catalyst for them learning the information instead of the escape room trap situation. For S&P it would so far only require one (i think) line to be slightly tweak to make it sound less like his heart gave out from sex after the events of Boxed In, to simple implying he died of heart issues before those events. And since the Boxed In MC has the history with his aunt and mom either way then even their flirting and pro-incest history clues wouldn't need to be adjusted.
But this is just my idea. I think it's a good one and solves all the issues some people dislike while also not removing anything that people who want the Boxed In girls like (unless the thing you find appealing IS the near NTR vibes of the new MC getting the old MCs left overs after his death) but I'm not unbiased.
