|This article is about a side arc character in Higurashi no Naku Koro ni.|
|This article is under construction and may be incomplete.
Needs content from Advanced Story added
Natsumi has short green hair tied into small pigtails and is frequently seen wearing a school uniform.
Natsumi is usually very easygoing. She tries to handle everything by herself, even if things get difficult.
Natsumi's family used to live in Okinomiya near Hinamizawa before moving to a new town.
- Kiichirou Kimiyoshi (relative)
- Akira Toudou (love interest, husband)
- Chisato Saeki (friend)
- Tamako Makimura (friend)
- Kuraudo Ooishi (acquaintance)
- Mamoru Akasaka (acquaintance)
Natsumi is first seen getting ready for school. Her grandma Aki asks her to pray to Oyashiro-sama at their altar before leaving however Natsumi ignores her. At school, Akira confesses to Natsumi that he likes her and wants to hear her answer later.
Natsumi becomes elated at his confession and when she returns home, she sees on TV that the Great Hinamizawa Disaster has happened, and many of her relatives still living in Hinamizawa and Okinomiya are dead. Aki tries to coerce Natsumi into praying to Oyashiro-sama again and becomes increasingly deranged.
The next day, Natsumi is locked out of her house when her parents go somewhere and she forgets her keys. She's soon approached by Ooishi and Akasaka, who ask about her knowledge of Hinamizawa and Oyashiro-sama. With many families from Hinamizawa suffering from ritualistic murders, Natsumi says her family will be alright but Ooishi gets incredibly personal and interrogative. Akira shows up to break up their conversation and pulls Natsumi away from them. She gets escorted home by Akira only to see her house covered in strange talismans, markings and paper effigies with her family's names written on them. Akira doesn't comment on the bizarre scene and leaves, making Natsumi worry that he'll see her as a weirdo.
Natsumi enters her house and discovers that Aki was the one to do it, believing it was necessary to avoid Oyashiro-sama's curse. Aki has also been drowning puppies in a bathtub as part of her ritual, and Natsumi hurriedly calls her parents to tell them of what's going on. Her parents tell her that all of their elderly relatives are going crazy, and Aki appears from behind and tells Natsumi not to worry.
The rest of the family try to brush off Aki's bizarre behavior, and Natsumi tells Akira the next day that her grandma is just crazy and lies that she is not from Hinamizawa. Akira accepts her explanation and later covers for her when other students are saying a Hinamizawan is attending their school, with Natsumi excusing herself and distancing herself from Akira despite his good intentions.
When she goes home she sees her mom Haruko stabbing Aki to death, and Haruko coerces Natsumi and her dad Touji into chopping up Aki's body and hiding it. Natsumi is visibly disturbed from having to perform such an atrocity, and her friends notice that something's wrong with her at gym class. They try to cheer her up by bringing Natsumi and Akira to a store but on the way they see a news report that a dismembered corpse has been found; Natsumi tells the group she left her keys at home and runs away.
Akira follows her home and wants to hear from Natsumi what's going on, as Ooishi comes by to ask more questions. Natsumi ignores both of them and enters her house, later witnessing Haruko beating up Touji for botching the corpse disposal. As Haruko goes off by herself to rant, Touji suggests to Natsumi that they go to the police before he suddenly gets stabbed in the throat by Haruko. Haruko then turns her attention to Natsumi and chases her throughout the house; Natsumi manages to call Akira over the phone for help, but when he arrives he gets knocked out from behind by Haruko. Natsumi struggles with her mom over a knife and soon kills her with it. Natsumi and Akira are rescued by the police, and Natsumi is sent to the hospital for a while.
Three days later, Chisato and Tamako show up at the hospital to cheer up Natsumi with cake and eat with her on the roof. Akira later goes to talk with Natsumi alone and reveals that he's talked with Akasaka and Ooishi about the truth: Natsumi killed her family. Shortly after Natsumi saw Aki drowning puppies, she pushed and accidentally killed her when she fell onto a table corner. Natsumi's parents didn't know what to do, and Natsumi was the one to suggest cutting her up and hiding her body. She then assaulted her dad when the corpse was discovered and later killed him. Haruko was the person screaming for help when Akira called the house, and Natsumi was the one to knock him out.
Natsumi freaks out and says she never wanted things to happen like this, and Akira hugs her. However, Natsumi stabs him and is soon restrained by security guards called by Akasaka and Ooishi. Akira is still conscious and smiles at Natsumi anyways, and Akasaka asks the guard to let her go; Natsumi gives Akira yet another hug.
Several years later, Akira has married Natsumi after freeing her from imprisonment; Natsumi had gone into the care of distant relatives of the Kimiyoshis and was locked in a room for years as she made talismans and ranted on about Oyashiro-sama's curse. Natsumi still felt guilt over killing her family, and Akira tried to convince her that he was the one to do it, however Natsumi knew he was just trying to ease her pain. Natsumi wants to make up for what she did but is aware that "the demon" will definitely kill Akira if it ever comes out again.
Natsumi is soon discharged from the mental hospital and goes on to live life with her husband happily.