Slow, and repetitive, graphic response. Hinders gameplay.

Since the range of reactions are quite limited, you could easily make these in pre-rendered video, spliced together, instread of 3d rendering; thus increasing the number of your players to the type that WOULD play this, and DON'T have high graphic gamer machines.

Also, while the heart targets are kinda nice, the roman numeral this in the second phase sucks... I real sec scenarios, I'm looking at the girl's face first, and to where her body is trembling or twiching second. Blushing and wetness are also interesting cues for arousal, but less obvious to represent in your chosen POVs. You have 3D models, so coding facial cues, twiching, redening due to irritation (as the X) and arousal blushes should be relatively easy.

And pre-filming all the new variants, still better than just dumping the redering on the client's machine.

...but I just checked and saw no implements of my (easy to code) suggestions on Sapphica, so I'm a bit disappointed and not expecting much here.