Relying on the dense protagonist is never a good move. The problem is that your not good enough to write clever things so your protag has to be extra dense to make up for it.
Prediction: the "slut" isn't a virgin (whatever), but I'm also guessing the seiyuu thot that is trying to fuck with him is an actual prostitute. It's just to cliched.
Honestly I agree with the younger sister that the mc sucks ass but I don't agree with her because I the female lead sucks too. If you're wondering why I'm still reading this I just read things I hate a lot.
Is that all these two do? Play porn games at school, after school and even together?
And they treat it as if it wasn't plain old JO material but some sort of high class literature with well written characters. I don't get it.