Fanart of Otetsuki. Source
Otetsuki (おてつき) is the protagonist of the game Yume 3kki ("Yoake from Yume 3kki").
Otetsuki has blonde hair tied in a side ponytail. She wears a purple sweater with a blue collar, an orange skirt, and brown shoes.
Otetsuki seems to be rather violent proven by her PC game ("Dieing") and her gun effect which can be obtained very easily, and that in the place where Otetsuki's gun is found, there is an NPC which resembles her being angry about her classmates from school bullying her. You can kill that NPC.
Not much is known about Otetsuki, but the NPC's that look a bit like her might be her classmates from school. She might have locked herself up due to fact that they bullied her. When trying to interact with those NPC's they do not talk, they just ignore Otetsuki. The truth is no one knows anything for sure about Otetsuki except for the author.