I tried it yesterday and I don't like Eric at all. as many of you already wrote, he has to much power and is an asshole, he is your typical angst NTR dude. at least theres a way to get rid of him, but its a bit stressful to do it and its not fun.
Of course its NTR, this because its a incest game and MC's "gameplay" is to seduce the mother and/or sisters. It wouldn't be NTR if the MC didn't have any "sexual" routes with his family. we could say this is Incest-NTR, this because the "player" is taking the role of a male with a purpose to get to know the females on the game, all which you can start a relationship with, Eric is there to stop it, cucking you using his influence and power. Not sure why this is so popular, I didn't enjoy it much.