Fun little game so far.
PROS: Nice art, and you can get to the lewd stuff early. You have a few choices as to your girlfriend's hairstyle and wardrobe, and you can take her out to various places and explore a little bit.
Talking with your girlfriend and getting to know her better pays off, as she'll ask you questions later on about what her favorite animal or color is. This in turn helps you increase your "good memory" score, though I'm not sure what effect that has on the game overall.
CONS: I like games where you can dive right in and start, but a short explanation about what the master key is, or if/how the good memory/bad memory score affects the game would have been nice.
Sex scenes are too short. They need to be longer. There's also an option to make your girlfriend orgasm multiple times, but it doesn't seem to have any real effect. Caring about your girlfriend's pleasure should lead to a more positive result for the player, such as more points towards the "good memory" category, more passionate sex from your GF, or a stronger desire for her to please you, or even just using stronger terms of endearment as your good memory score increases.
Finally for the sex, a full view of her cum facial would be nice. Right now it's just an extreme closeup of her eyes and nose.
The option to cum other places, perform cunnilingus, try anal, etc... would also be welcome progressions in future installments.
Anyway, overall a nice start and I hope to see more.