Saiko-chan

Saiko-chan, also known as Saiko, is the titular antagonist of Saiko no Sutoka. She is a high school student who has an obessesive relationship with Akira, The main protagonist.

Background
Saiko seems to be a normal, diligent High School girl in a generic Japanese High School in a small city. She suffers from some kind of mental ailment, presumably DID (Also known as Dissociative identity disorder), making her mentally ill, violent, and sociopathic. So far, the story tells that she has a crush on a boy, Akira, A.K.A, her "Senpai". One day, she starts getting frustrated that Akira seems to focus a lot more on his friend, Shinji, and fails to notice her.

Either because she simply could not stand Akira having other friends or just because she imagined a boy-love romance between them, she enters into a psychotic episode, trapping (or killing him in Yandere mode's good ending) Akira's friend during the evening as she drugs and ties Akira up within the school during the night. Desperate and deranged, Saiko sets up a death game during the night in an attempt to play a morbid cat-and-mouse revenge game with Akira.

Name origins
Saiko-chan's first name is play on term "psycho," referring to her as a crazed maniac, and psychotic personality. "Saiko" is also an actual Japanese name. The kanji in her name 最 (sai) combined with 子 (ko) translates to "the greatest child". Her actual name is never specified but the creator of the game has stated that her given nickname is "Saiko-chan".

Appearance
In Normal Mode, Saiko appears to be a high school student with short, unkempt auburn hair with scarlet glowing eyes. She wears a white buttoned shirt with a pleated navy blue skirt that has blood all over including on her face, arms and legs and goes barefoot. She also carries a bloody knife.

In Yandere Mode, she appears to be more normal looking. Her (now brown) hair seems longer and neater wearing it in low pigtails, wears round glasses, a yellow vest underneath a white shirt along with a purple skirt and black loafers.

In Yangire Mode, her appearance seems slightly similar to Normal Mode except she wears a black bunny costume with a bloody grin smeared around her mouth. Her eyes and the smeared grin appears to be glowing brighter and creepier too.

In Nightmare Mode, her appearance is similar to Normal but includes the fact that her sclera is completely pitch black but her scarlet red eyes remain the same except it is far brighter. Blood is seemingly coming out of her eyes and her body is covered in glass shards. Notably enough there is a scar residing within her stomach in which she was impaled by the glass shards during the good ending where she dies. This mode is the trigger of Akira’s PTSD and his Nightmare as the title of the game mode may suggest. Akira’s nightmare manifests a supernatural form of Saiko after the incident thus explaining the abnormalities within her appearance. She's also somewhat darker than Bunny Saiko from Yangire Mode.

Personality
Saiko seems to suffer from Dissociative Identity Disorder (DID), based upon her tendency to switch between personalities at random times throughout the game, heavily dependent on the game's current difficulty mode and her current mood towards Akira, which can be changed by performing actions such as (but not limited to) stealing her keys and being low on health in close proximity to Saiko; For example, the former action will cause Saiko to become hostile towards her Senpai, while the latter seems to bring about her more gentle and "normal" personality, as she may sometimes offer the player a healing item to restore their health, even mere moments after causing the player's damage herself.

Normally, she is a psychopathic murderer, manipulator, and has a taste for seeing someone suffer. Her sadism also comes around when she feels the need to “punish” Senpai after being angered by him running away. Despite her love for him, Saiko seems to enjoy putting him through pain. On occasions, she gives a false sense of security to the protagonist in order to trick and hurt him. An example of that is when she pretends to be guilty of her actions and offer “Medicine”. Though at times she does actually give medicine, she can also offer a fake that will lower the Protagonist’s health.

On special moments where she feels empathy, she is kind and loving, offering medicine to the protagonist after injuring him and claiming she is sorry. When that happens the player will have to be careful to trust her, as she is faking it sometimes. When her feelings are genuine, she will refrain from attacking the protagonist.

during yangire mode, on Normal mode, do not expect to win her in a game of rock, paper, scissors If you get captured, it's rigged, I would advice keeping a eye out for ellisu since she has the tendency to camp floors which you may approach.

Observation
As the updates on Saiko A.I. go, the more blurry the border between Saiko Personalities is.


 * Both personalities seem to adopt traits of one another: Her "tame" personality often acts extremely violent, going as far as intentionally poisoning the Healing Pills that she provides to Akira, and even in the late-game, fatally back-stabs Akira on sight (even at full health).
 * She also instant-kills Akira for attempting to peek under her skirt, proving that her "love" for him has clear limits
 * In Yandere Mode, she kills Shinji being on her "tame" personality if he defies and refuses to follow her instructions, going as far as she will sport a gas mask and start throwing poison bottle at him
 * In the contrary, sometime her "Angered" personality can show strange signs of mild companion, as she often gives 5 seconds to escape, accept to give up on her chase if Akira wins her shifumi round, and stops her assault as Akira gives her the Diary.
 * Sometime, she does physically fakes shifting back into her "Tame" personality (when she is petted to be calmed down, when she provides fake medicine and at random when the Diary quest is completed), making it very suspicious her "Tame" persona is actually somebody else than her "Angered" one.

Saiko's "split" behavior could be interpreted in a few different ways:


 * Saiko really does suffers from Dissociative Personality Disorder, but both personalities work in teamwork and one another takes fully control depending on her emotional state. While "Tame" Saiko does seem to not be particularly hostile to Akira and might even delay his death, she clearly doesn't try to stop "Angered" Saiko from perishing him. Also, both personalities see Shinji as a nuisance to be eliminated before Akira wakes up. As Akira manages to avoid her and progressively gather the escape code, "Angered" Saiko looks a lot more prone to spontaneously take control, hinting that her frustration of losing alone is enough to decide who is mainly in control.


 * Saiko could "simply" be a single-soul psychotic, paranoid, bipolar and sociopathic girl suffering from acute Intermittent Explosive Disorder, but is also somewhat really in love with Akira, yet not enough to overcome her frustration and anger-fuelled psychotic violent episodes. Unable to really understand herself about her outbursts of rage, she might interpret them as another persona in order to convince herself or others of her actions. Her glowing irises would then be simply a hint of her level of blood pressure when she is overthrown out of her general reasoning and gets bloodthirsty and not actually a sign of full personality shift. The more Akira manages to evade her, the more her blinded rage episode occur, the more her explosive episode will happen.


 * Yangire and Extreme Yangire (and possibly newly added Nightmare) modes could also brings out an insane supernatural explication to her psychotic behavior, as Saiko seems to have been so far a diligent student and it is sort of hard to believe normally such extremely ruthless, manipulative, sadistic, bloodthirsty and sophistically vicious behavior would suddenly appear to a girl having reached mid-high school without prior notice from the school staff. Saiko might very well be actually possessed by an evil spirit trapped inside the school, making her lose her global empathy and increasing her manipulative nature, shifting from medium control over Saiko in her "Tame" persona, to full control in her "Angered" persona. It could have taken advantage of Saiko when she went distressed as Akira would not notice her. This is enforced by a few hints: - The game happens in Japan, where mythology about evil spirits manifestation after school hours inside every town schools is pretty rich. Some spirits needs vulnerable kids to manifest themselves, and are often here to cause misdemeanors. - Yangire and Nightmare maps outlook does not look natural, as blood swells from the walls and everything looks unnaturally decaying. The darkness is insanely and unrealistically thick despite the clear night sky, a common trope when a curse occurs inside a school within Japanese fiction. - Saiko and Elissu eyes glowing mechanic is not possible in real life as human do not have a reflective retina like cats. However, in Japanese mythology, possessed humans often have a physical transformation of their eyes. - Saiko's supernatural appearance evolves as the night goes, as at sunset she barely look other than cunningly psychotic and savage, at dead of night, Saiko look straight-up possessed. - Admitting Nightmare mode is not a PTSD nightmare of Akira post-normal gameplay, this seems to confirm the school is prone of spiritual manifestation.

Trivia

 * It is not actually clear if Saiko plans to commit suicide if Akira/Shinji manage to escape, or even if she will after murdering both, or simply plans to mop up and get away with the murder. However, if Nightmare mode were to happen post-game, then it is very likely that Saiko is planned to die in the normal canon endings and end up haunting the entire school afterward.
 * Her overall disregard at leaving evidence behind such as destroying school equipment, poorly hide her misdeeds, letting live CCTV cameras film herself wandering around the school blood-drenched and probably leaving her own blood and fingerprint everywhere in the weapons and off-limit equipment seems to indicate she doesn't plan to get away with it as covering up everything would be impossible within a single night alone.