If you're here for the porn, this is a 5/5 experience and I highly recommend you try it.
DECOY has some of the highest-quality animations on the website, with spectacular sound design enhancing the scenes.
However, I almost felt like giving this game a lower score, because the actual gameplay is more like a 2/5. You spend the majority of your time slowly dashing through similar-looking mazes, usually ignoring the enemies because there's no point in fighting them. At the end of the mazes, there is always a boss who somehow manages to be simultaneously too easy and too confusing. It'll take you a while to figure out how to even hurt the boss, but at least you'll never be dying and reloading.
I also can't comment on the story. I've never really had the patience to wait for the MTL translation to kick in, and this was an example of a fairly mediocre translation that had issues with text being cut off. So... don't expect a coherent story, but I also won't hold that against the game in my rating. I basically made up my own story in my head and that'a always fun sometimes.
So why 5/5? At the end of the day, the game looks great, it's not too hard, and the platforming stages are never too long. If anything, the meh gameplay only serves to pace the large number of high-quality sex scenes. I could see myself booting up my completed save of this game every so often just to revisit the animations and that's extremely high praise from me.
If I were to criticize something about the sex scenes, it's their "inefficient" delivery method. After every dungeon, you may unlock the next tier of sex scenes with a certain character, so in some instances, you may unlock 3–4 blowjob scenes with a single character, and going through these one-by-one is a little weird. I feel like these scenes could have been delivered in a more seamless way that connects them together to form a long sex scene rather than isolated animation loops that you access from a menu. But again, the quality here is so absurdly high that it's hard for me to complain too much. It's not like I'm not going to fap to these scenes.