Very suspenseful! This visual novel really nailed an unnerving atmosphere. Here's part 1 of my full playthrough, if anyone's interested:
What I liked was the ambiguity of your relationship with your so-called girlfriend, so it kept you invested in finding out what was truly going on. The visual and audio design also made everything feel slightly off and was a great complement to the story.
The only element that I felt was not to my taste was the few times where a scene was overly described as if it was a book. Like when Nagi's every physical feature was explained in the beginning, even though her clearly drawn sprite is right in front of you! Sometimes it added to the tone of the game if done with purpose, but other times it felt unnecessary to me. But that's just my own subjective preference, I know others would disagree with me.
Anyhow, it's a great horror visual novel! I can see the inspiration from Charon's games, but it definitely has its own twist to it.