Corpse Party D2: Fatal Operation
Naomi and Seiko finds her diary in one of the rooms and it reveals that Machi had a friend named Hideo, who was a classmate with Shinozaki. Machi and Shinozaki both were talking about the latter's family, until one day Shinozaki cursed Machi, which made her sick. At first both Hideo and her brother don't believe her, until her hair turn white, which starts to worry her brother. Hideo left her to marry Shinozaki. The last entry says that Machi's brother did something bad to her.
It is revealed here that Machi and Doctor Fuyu Hirata are siblings. Naho then explains that Machi and Fuyu both died in the basement of Devine Blessing Hostipal about thirty years ago. They were both strapped to a device that most likely killed them both, sadly it couldn't be examined.
Machi makes her first appearance in the beginning on this chapter. After Seiko runs inside her room she sees Machi. They both talk and Machi attacks her, hoping to steal her body from her. Seiko then runs away, but slips and falls in the hole. Machi laughing that she can still use her.
Machi's appearance differs in this chapter depending on the choices of the player.
If you decide to skip the searching for more clues Machi appears as a possessed Seiko and after appeasing Fuyu they all escape. After that "Seiko" stops talking to Naomi.
If you decide to stay and find the rest of the clues, you will see the added event of Seiko escaping from Machi, And makes her last appearance in the main hallway, right before the group can escape. She enters Naomi head, hoping to possess her, but then sees Naomi's memories, which brings her back to her senses. Machi then lets everyone leave to their world, and moves on to an afterlife.