Chuckle*
There are sine ubcibsustebcues wuth your post Jedily, a few of thejm are trifling and not at all a problem - but some of them are rather major.
1. Aito's last name is not Haru, Haru is the username of the player who plays Aito. xD
2. The arms in the mirror are ethereal and translucent white, not rotting (this is a minor offense, I actually liked your description better than my own)
3. The screams of the children from beyond the mirror are not limited to affecting only Shiori - everyone in the same hallway as her can hear them, and the're very loud, conversation is all but impossible unless you're shouting into the other person's ear. (Major issue)
4. That last text-message on Kaku's cell phone was rather long... xD (Not really an issue)
Other then that, you seem to have a pretty good idea going there, about the mirror I mean. ^^