Who do you think you're talking to, little girl?! I'll ring your damned neck just to watch you squirm! ~Teacher
Shinozaki was often alone and didn't have any real friends. In fact, she enjoyed the solitude, and she often stayed after school and watched the rain.
One day, as she was doing so, her teacher approached her under the pretense to talk with her, but his true purpose was to rape her.
Shinozaki was unable to escape, and thus she blackmailed him that she will tell about this to everyone else. The teacher continued to mock her, saying that nobody would believe a lonely girl with no friends.
Shinozaki retreated to the ledge of the third floor inter-connecting corridor and, as the teacher approached her, she yelled that she will throw herself to her death if he tries to get closer.
The teacher ignored this threat and Shinozaki ends up losing her footing, falling off the third floor corridor to the courtyard below, killing her.
Shocked at what just happened, the teacher tried to hide her body, but the principal discovered him.
Under the pressure, the teacher confessed everything to the principal who, unwilling to ruin the school's name, helped the teacher bury Shinozaki's body.
She was reported missing, as her body was never found, and soon everyone had forgotten about her.
Out of revenge, she recreates the school in another dimension and starts kidnapping countless children, killing them in the cursed halls.
Somewhere along the lines, Shinozaki splits into two personas, the first one being full of hatred and resentment, while the second one is actually good.
After Ayumi Shinozaki and Yoshiki Kishinuma manage to escape the school, the good Shinozaki approaches them and explains her story, as well as the way to save her friends.
At the end of the game, she helps Ayumi and Yoshiki reach and appease the vengeful Shinozaki.
In one of the scenarios, if Naomi Nakashima is sent to the toilets to accompany Yuka Mochida, the vengeful Shinozaki will take her body and tag along with Satoshi Mochida and Yuka, pretending to be Naomi.