|“||Naomi? Are you there?! Answer me! Please! ... Naomi! Please, just let me hear your voice! *sob* ... Please... Just say something! I'm your mom, Naomi! God, please...don't let anything have happened to her!||”|
—Natsumi Nakashima, Corpse Party (CHAPTER 3)
Natsumi is an adult woman with average height and weight. She has long brown hair and hazel eyes. She wears a white long sleeve shirt underneath an eton blue puff sleeves dress and a teardrop shaped necklace.
Natsumi is a teacher at a nursery school in Tenjin. She was widowed eight years ago when her husband, Naoyuki, was killed in a traffic accident in front of their house. She has raised Naomi since then with kindness and a little bit of severity. She is good with handicrafts, and used to knit socks and sweaters for Naomi when she was little; knitting things like stuffed dolls made Naomi happy. Natsumi is a popular teacher at the nursery school, and both children and parents call her "Ms. Natsumi" (夏海先生 Natsumi-Sensei ).
Natsumi can be heard briefly in the prologue where she calls Naomi while she is inside Heavenly Host Elementary School. Unfortunately, Natsumi is unable to hear her daughter's voice and begs that nothing has happened to her.
Corpse Party: Book of Shadows
Natsumi is seen at the beginning of Corpse Party: Book of Shadows talking to a therapist about Naomi over the phone. Naomi has been acting strange lately, talking about Seiko Shinohara, who Natsumi thinks is Naomi's imaginary friend. The therapist tells Natsumi to support her daughter while she's like this. Thus Natsumi heads up to her room, where Naomi is found standing in a corner.
Natsumi tries to talk to Naomi about a cat she saw when she was out shopping, attempting to start a conversation. Naomi remains silent, so Natsumi asks if there's anybody there in the corner. Naomi responds with, "Seiko..." Reluctantly, Natsumi asks her about Seiko, with Naomi giving short answers. After a few questions, she brings up that no matter which classmate she asks, none of them believe Seiko exists, and Naomi gets mad, kicking her out of the room. Natsumi tries her hardest to calm her down, but Naomi continues her rampage. Eventually, she manages to give Naomi some medicine to calm her down.
Episode #1; 『Seal』
Natsumi is seen at the beginning when Seiko sleeps over. She calls them for supper and while eating, they talk about Naomi's crush on Satoshi and plan on hanging out to talk one day. Natsumi then suggests them bathing together, which Seiko forces Naomi to do. The next day she tells them goodbye as they head off for the culture festival.
Corpse Party: Blood Drive
CHAPTER 03 『 Pain 』
Taking care of Naomi who keeps persistent about "her imaginary friend" has taken its toll on Natsumi's psyche. Natsumi acts more aggressive towards Naomi. After Naomi's left eye was struck by a curse, Naomi screams because of pain. Natsumi rushes to Naomi's bedroom, thinking Naomi is faking it. She yells at Naomi to drink her medicine, but Naomi screams in pain and tells Natsumi that her eye is in pain. Natsumi angrily tells her to show her eye, and she sees the word 'Sachi' in hiragana in her eye. Shocked and scared of what she just saw, Natsumi leaves Naomi's bedroom, ignoring Naomi's crying for her.
As Naomi leaves her bedroom, she peeps on Natsumi sharpening a knife in the kitchen. Feared of what her mother planned to do with the knife, Naomi leaves her house.
CHAPTER 04 『 Pillars of the Six Demons 』
Naomi is walking toward her house when she accidentally sees Natsumi clasping the arm of a young man in a construction outfit, cuddling up and kissing him before they both are out of Naomi's sight.
Corpse Party: Tortured Souls
Episode 4: Sorrowful Truth
Natsumi is seen at the scene after credit, talking to a therapist over the phone. She is crying over Naomi who keeps talking about Seiko Shinohara, who Natsumi thinks is Naomi's imaginary friend, and how Naomi gets mad when she talked to her about it. Natsumi cries, asking what happened to her daughter. Meanwhile, Naomi is staring at the window in her room with blank expression and muttering inaudible things, presumably about Seiko.
- Natsumi is one of the two characters who doesn't have a sprite in Corpse Party; the other one is Yuu Shinohara.