I really liked this little comic. I'm not sure if I properly understand the story being told here, but at the same time it's fitting considering the game that it's based on.
My interpritation is that in this world, certain people can travel between dream and reality like they are alternate worlds (I assume because of that one scene where they exit the class room and go into the warped library, and the scene where they jump into a portal into the aztec monkey room). One day, one of these people enter the dream of Madotsuki (I forgot her name so I will just call her 2kki). Madotsuki is shy and reclusive, so after discovering someone just like her, she attempts to befriend her, but 2kki is too closed off and rejects her efforts. After escaping the monster toriningen however, Madotsuki learns where 2kki lives after seeing it during their escape. Using this knowledge, she travels to her house and saves her life just in time, thus making it so that their respective "endings" don't happen (and I assume they become friends after that). Not sure if I got it all right but that's just my interpretation.