To be fair, I believe the Dev. Why would they add that and NOT call it NTR if they knew what it was? That sounds counter intuitive. We've been spoiled I think to believe that easy "slutty" girls are faithful to you and only you. Even the most mainstream games with these kinds of characters rarely talk about other men. In this game, she has a fling with you, and then goes with another dude. To us it's NTR because we never got a direct warning that she isn't a Love interest so it stings. However, again, I believe the Dev when he says they didn't intend for her to be a LI. It's just unfortunate for us because we already saw her that way :/
I imagine the romance is gonna be with Lucie. The dev already stated both publicly and privately that no NTR is gonna happen.
The Endings so far are gonna be:
1, Lucie Only (True Romance)
2. Lucie but you strayed with other women
3. You lose Lucie because she found out and hates you.
So it's clear both from the name of the game and the Dev's direct words that it's focused on Lucie and the inconsistencies like Lucie being kinda slutty are being changed/already changed.
Don't be too harsh on the Dev. It takes a village. His game can look really good if we help build it up