Oh this was so interesting! I like how no matter what happens or what choice you go through, the loop is already established. Even if you choose different doors at the start, it's already cemented in the story what happened in chronological order and that there was no hope for a different ending (at least, from what I could try and find). I like how there was hints of something going on beyond what we expected from the opening MC gave us. Lady Pink really went overboard and revealed interesting things about this endless situation we find ourselves in.
I'm curious if that key would have been a sort of gateway into the world Lady Pink resides in, not sort of an exit to MC's world but to a different world itself. Still, this was quite the nice little visual novel even though my eyes did burn a bit from the amount of pinks that were being shown.