Satsuki is a teenage girl of below average height and weight. She has short brown hair with longer bangs at the front and green eyes. Just like the other students of Kisaragi Academy Junior High, Satsuki wears a blue smock with a white collar flap and a small pink bow attached, knee-high white socks and white shoes with yellow soles. She also customized her uniform to have a pink bunny with crossbones on the left side of the dress. Several pockets are presumably sewn under her skirt, in which she carries several of her favorite potato chips packets.
Satsuki is Yuka Mochida's classmate and best friend. She is an airhead who doesn't seem the least bit fazed when she arrived at Heavenly Host Elementary School. She always carries around a bag of potato chips. Satsuki is much more cheerful than Yuka and a little perverted like Seiko Shinohara. She also enjoys teasing Yuka, and calls her "Yukes" (ゆかち,Yuka-chi?).
Satsuki Mizuhara is the result of Spiritual Surgery, a transformation experiment conducted by Martuba's Tomb by combining two individuals: Satsuki Nekoma and her friend, Harue Mizuhara. The surgery enables her to assume a "monster form," which is sealed and controlled by Magari Mizuki with Synapse. When the control breaks by other means, Satsuki will go berserk and devour anyone within her line of sight, unable to suppress her appetite.
In her "monster form," Satsuki splits her head into eight equal parts, revealing a giant mouth with rows of sharp teeth and jaws strong enough to tear apart and devour one's head within seconds. This ability mirrors Harue's physical condition - shattered, split open jaws after having a car accident.
The surgery did not only affect her physique, but also affected her personality. Satsuki inherited the personality of her friend, Harue.
As Satsuki Nekoma, she was an introverted and a passive child. She mistook being beaten by a frying pan as a form of love from her parents since they never really cared about her, devoting their lives as members of Martuba's Tomb. She also loves potato chips, which are abundant in her house and eating them made her mother a little bit happier.
Harue Mizuhara was the total opposite of Satsuki. She is cheerful and outgoing, trying to cheer Satsuki up. She's also shown to have a somewhat perverted side, with her commenting Satsuki to flaunt her "assets" more so she looks more attractive to boys their age.
Satsuki is bathing with Yuka at "Mochida Springs". She greets Satoshi when he enters the hot springs and warns him to not stare at her breasts, and starts to jiggle them, which Satoshi yells at her to stop. Satoshi's mother offers drinks to Satsuki, Yuka, and Kuon Niwa, which they accept enthusiastically. Satoshi's mother then takes a picture of Satsuki, Yuka, Kuon, Satoshi, and Naomi Nakashima to commemorate Mochida Springs' establishment.
CHAPTER 05 『 Breakdown 』
Satsuki and Yuka walk to Kisaragi Academy in the midst of stormy weather, but when they arrived there, the school is temporarily closed. Satsuki complains about how Kisaragi did not inform them about such crucial information. Yuka asks Satsuki if the same thing ever happened before in her old school, and Satsuki says that it has not and her old school has a better communication system. Satsuki then asks if she can go to Yuka's place for a dip at the springs again, but Yuka is concerned that Satsuki's parents would be worried if she did not go home soon. Satsuki cheerily answers that her parents are pretty hands-off with their parenting, and jokingly says they might have given up on her.
Suddenly, Misuto Kiriya approaches the two girls and informs Yuka that Satoshi has gone to Heavenly Host Elementary School, and he is in grave danger. Satsuki tries to reason with Yuka that she should not trust him, but Yuka believes in Misuto's words since he knows about Heavenly Host and Sachiko Shinozaki. Satsuki then reluctantly decides to come along with Yuka despite she doesn't trust Misuto a little bit. Misuto warns that if Satsuki is lost in the Nirvana, he will not search for her, but Satsuki doesn't care and warns him that if he ever does something weird to Yuka, she would bite him.
CHAPTER 06 『 Book of Shadows 』
CHAPTER 08 『 Ties Severed, Ties Mended 』
Misuto runs after he punched Ayumi and took the Book of Shadows with him. He then ran into Satsuki who's together with several Red Helms behind her. Misuto is surprised to see her and wonders what she's doing there and what happened to her guarding Yuka. Misuto attempts to run and pass Satsuki, but suddenly her head splits open, revealing rows of sharp teeth, which bites off Misuto's head and devours it. Magari Mizuki then approaches Misuto's corpse and takes the Book of Shadows from him. She then reveals that the Satsuki is a member of Martuba's Tomb. Satsuki is crying and panting, but Magari grabs Satsuki's hair and pulls her in. She warns the 'monster' to stay with Yuka, and Satsuki responds obediently to her mistress. Satsuki and Magari then walk off with Red Helms following them.
CHAPTER 10 『 Reparations』
Satsuki is seen laying unconscious beside the also unconscious Yuka. Yuka then wakes up and asks Satoshi if both of them are okay, to which he responds Satsuki still hasn't woken up. Satoshi, Naomi, Yuka, Yoshiki, and Aiko run together to escape from the collapsing Nirvana, while Magari escapes together with Satsuki.
EX CHAPTER 07 『 Satsuki's Heart 』
The chapter opens with Satsuki narrating that she doesn't remember much from her childhood, but she remembers her parents being very "kind". Her childhood home was very dusty, she compares it to an empty void and day by day less and less furniture remain in her home. Satsuki complains to her mother that she's hungry, and that the power is out. Her mother then repeatedly smacks Satsuki on her head with a frying pan while apologizing over and over. While this is going on, Satsuki narrates that this happens to her all the time, and right after these outbursts her mother would burst into tears and give Satsuki a bag of potato chips. That is why Satsuki loves frying pans, because she never felt true love from her parents so she mistakes this for love from her parents. Satsuki's mother announces that tomorrow Satsuki will be apart of a great experiment for Martuba's Tomb, and gives Satsuki a bag of potato chips.
Tomorrow at school, Satsuki meets up with a girl named Harue Mizuhara, the closest person Satsuki has to a friend at her school who always smiles and is upbeat. Satsuki turns down an offer to hang out with Harue because she has to go to Martuba's Tomb tomorrow. Harue, doesn't hesitate to express her disdain for the cult, and says that it should just be Satsuki's parents that have to attend those meetings. Later that day, Harue gets into a car crash and her jaw is broken-preventing her from ever smiling again.
The next day, it is time for the spiritual surgery. Satsuki is wearing nothing but a black wardrobe and is very cold. Magari Mizuki asks Satsuki if this is really what she wants to do this. Satsuki then notices the decapitated head of Harue Mizuhara in a bowl and a momentary moment if human weakness, starts crying and says she doesn't want to do this. Her parents are disgusted by Satsuki, but Magari slices her parents so their upper half fall off and die. Magari promises to make Satsuki her pet and to arrange "replacement parents" for her and to live her life and enjoy it. Magari then announces for the spiritual surgery to begin.
From the surgery, an entity named Satsuki Mizuhara is born, a combination of the two girls - Satsuki Nekoma and Harue Mizuhara.
Significant plot details end here.
Satsuki was originally going to be a main character in Corpse Party 2: Satsuki's Heart; she was written as being a daydreamer and best friend of Yuka. However, since that game was eventually abandoned, Satsuki was never seen again until Corpse Party 2U.
One of the extra chapters in Corpse Party: Blood Drive is titled "Satsuki's Heart", a tribute to the canceled supposed-sequel of the original CORPSE-PARTY for PC-98.
Satsuki ended up inside Heavenly Host, like Haruyuki Inumaru and Aiko Niwa, because of her relationship with the other characters who ended up in the school.
Her real surname, Nekoma, means "source piece" or a "pawn" in Shogi (Japanese chess). In the English version, her name is translated as "Satsuki. My pawn." as if Magari addressed Satsuki as her pawn. The surname itself is rarely heard and used.
Satsuki's "monster form" might be inspired by another series, Parasyte.
#0; Hysteric Birthday!, #1; The Shame on The River Kwai, #3; My Greatest Feeling! Trans-Abandoned Bomb Shelter Ultra Quiz, #4; Crying Out Love, In the Center of Heavenly Host?, #6; Aluminum Chef, #7; Repentant Reals Go to Hell, #8; Today's the Day, Farewell