Arata Shoto|Arata ShotoThe protagonist of KTJ: SG. He's just a normal high school student who saved upperclassmen from a fire at his school. He is part of the Detectives, and his identity is Arata Shoto.
- Amateur Sleuth
- Crime Magnet: So far, he's attracted the affection of King and Glasses, two serial killers. Aaaand, even Flare, who's probably the most dangerous of the bunch.
- Did I Just Say That Out Loud?
- Even the Guys Want Him: Two most prominent ships are with King and Glasses, and Romeo describes him as "cute for a guy".
- Heroic BSoD: When King dies, he loses the ability to hear anything else going on around him, making for a lot of censored dialogue. He then passes out. He's out of the protagonist seat for the next chapter, and doesn't even appear for the first three updates, and is only mentioned.
- Idiot Hair: He has two ahoges on his hair.
- I Gave My Word: Promises Diamond to bring her to the ocean when they leave.
- The Protagonist: He is the protagonist of the story. It's even his codename!
- Understanding Boyfriend
???| EdogawaA bright girl who loves girls and kogal fashion. She is the first person that Protagonist meets in the manor, and one of his best friends there. She claims to be a detective, though her identity is not confirmed yet. However, Syringe affirms that Killer is a detective, though doesn't specify which when he confesses his own identity. Later on, Butler-kun confirms Killer is Edogawa publicly, while also confirming Syringe's identity.
- Beauty Mark
- Cute Bruiser
- Eat the Rich: Her response to King talking about his financial situation.
- Femme Fatalons: According to Protagonist - Killer has incredibly sharp nails.
- Girly Bruiser: Despite not claiming to be strong, she's punched King the most in the manor.
- Gyaru Girl: A kogal.
- Lipstick Lesbian: Incredibly gay femme.
- Only Has Same-Sex Admirers: Understandably so, because she's a lesbian.
- Valley Girl: Like, often says like, in her like, sentences!
Yahiro Amane|Lover BoyOne of the more troublesome characters in the mansion, however, Protagonist has earned his affection and devotion, much to his ire (or so he claims). He is part of the Serial Killers, revealing his identity to Protagonist during his free time. His identity is Lover Boy.
However, he is framed for Collector's suicide in CH 2 by Maid-chan for getting "too close to the truth". He is unceremoniously blended, even though he was not the culprit.
- Abusive Parents: Hinted at by Sol and confirmed by Word of God that King's parents were incredibly abusive towards him. It's also implied that the Evil Matriach of his family, wasn't his mother, but his older sister, leading for a fear of women due to the nature of her abuse.
- Asshole Victim: Sure, King wasn't the culprit of the CH 2 death, but it's hard to feel bad for him, even when he's falsely executed on account of his Monster Misogyny.
- Cool Shades: Rarely takes them off.
- Hates Being Touched: But only by women. Word of God also confirmed that one of the secrets on King's ID was that he can't stand it when being touched by a woman.
- Idiot Hair: Known to spring back up even when combed down as well.
- Monster Misogyny: In fact, he hates them so much, he kills them.
- Red Eyes, Take Warning: They're pink, but... close enough.
- Serial Killer: Revealed in his chapter one freetime that he's the serial killer, Lover Boy.
- Slasher Smile: One of his default expressions.
- Socialite: His family is VERY rich and well known.
- Sunglasses at Night
- Very Punchable Man: His being punched counter is over 5, and it's only chapter one.
???| Enoh Universitys RipperA young man whose enigmatic behavior and somewhat reclusive ways sometimes get him into trouble. He and Protagonist have a very good relationship. A very... gay relationship. He is part of the Serial Killers, despite being a former serial killer. He reveals his identity to Protagonist at the end of the prologue and seems to regret his actions deeply. He is the first confirmed identity besides Protagonist's. His identity is Enoh University's Ripper.
- Badass Bookworm
- Serial Killer: At least, a former serial killer. Revealed at the end of prologue that he's Enoh University's Ripper.
- Smart People Wear Glasses
- Stoic Spectacles
- You Gotta Have Green Hair
???| DollyThough trying to assert himself to be the leader-type of the group, he is usurped by Protagonist in popularity. The two hold a disdain for each other. He is part of the Detectives, revealed during the CH 2 Revelation Ceremony that he is Dolly. However, soon after that, he ends up the CH 2 Victim. It is later revealed that though King is executed, his death was a suicide.
- The Collector
- Gay Moment: Has one of these at dinner with Protagonist, Syringe, and Flare. He admits that's he's indiscriminate with what type of boys he likes. Ironically, this is one of his last moments, and his last spoken line is "Boys are nice."
- Great Detective
- Hates Being Touched: He constantly wears a full body wetsuit under his clothes because he doesn't like the contact of food against skin, or others touching his skin either. He's the type to eat pizza or fries with a fork, like Syringe.
- Jerkass: Though, after the CH 1 trial, he starts to warm up to Protagonist, and is revealed to be a kinder person.
- Kitsch Collection: Like his name implies - he is a collector. And we later find out, he collects porcelain dolls - and is the famous detective Dolly.
- Meaningful Name: Another mothy reference, this time to Gallerian Marlon, known also as "Collector". It also happens to be a reference to his Detective persona - Dolly.
???|???An upbeat and perky girl who seems prone to fits of strong emotion. She's passionate though, and gives everything her all.
- Break the Cutie: It's revealed during the trial that she was planning on killing, and Valkyrie, the true culprit, usurped her plan to kill in order to protect her. She gets significantly broken after the trial too.
- Breaking the Fourth Wall: In CH 3-3, she makes comments towards Romeo for breaking the fourth wall, despite it usually being Maid-chan's job, while breaking the fourth wall herself.
- Genki Girl
- Goth Girls Know Magic
- Light Feminine and Dark Feminine: She's a preppy goth, wearing a black and red seifuku, to Valkyrie's lighter color scheme.
- Lipstick Lesbian: High femme lesbian.
- Perky Goth: Almost prep-passing.
- Zettai Ryouiki: Grade B.
???|???Sol's younger brother, a genius with technology, though he seems to be a little abrasive and more than a little eccentric.
???|Masquerade ButterflyA strange-tempered girl who moves to the beat of her own drum. She's prone to daydreaming and seemingly unobservant. Despite this, she's one of the Detectives. She reveals herself to be Masquerade Butterfly to Protagonist after the Revelation Ceremony.
- Break the Cutie: Between getting her fingers cut off in the prologue and her best friend's death in chapter one, she's getting rather broken.
- Cat Smile
- Every Girl Is Cuter with Hair Decs
- Girls Love Stuffed Animals: During Rabbit's free time, he was seen gathering some for her.
- Magical Girl: Or, a wannabe. She's Masquerade Butterfly - a magical girl detective!
- Meaningful Name: She says it's not like the season, but a clockwork's spring. Word of God also confirmed this is another mothy reference.
- Verbal Tic: Puwa~!
Hifumi Sena| DimlightA supermodel who prides herself in her punctualness and schedule. She can be icy at first, however, once you win her respect, you gain a loyal ally. Flare reveals that ID says she is Dimlight during a CH 2 freetime, however, she claims to not have the memory to back this up, and is horrified with herself that she could've possibly done such a thing.
- Being Tortured Makes You Evil: Oh, you know.
- Diabolical Mastermind: Collector's suicide note reveals in the last line that he remembers that she was the Director. Whether or not she actually is has yet to be confirmed, but Bled seems to be starting to remember some of the horrible things her sister has done too...
- Fiery Redhead
- The Glorious Warof Sisterly Rivalry: With Bled. She's the pretty one. Though a little while back, it was a case of Cain and Abel...
- Identity Amnesia: Flare reveals to Protagonist that despite her ID saying that she is Dimlight, she cannot remember doing anything of the sort at all. She's torn up by what she could've done in her past, and what she feels now. Protagonist suspects that she has Repressed Memories as well.
- Idiot Hair: Not shown in canon, but in other artwork to be hidden underneath her hat.
- My God, What Have I Done?: Flare is... heavily conflicted with the atrocious things she's been hinted at and outright stated to have done in the past.
- The Protagonist: But she only takes over for a part of Chapter 3.
- The Fashionista: She's the youngest model to have been on the cover of Vogue.
- Slasher Smile: In CH 3-2, despite claiming she doesn't remember ever being the Director - she's depicted making one of these, with her Face Framed in Shadow.
- Third-Option Love Interest: Is implied to have a crush on Protagonist, however, isn't one of the main two love interests.
Coco Dyer|Bloody MaryA super-pessimist who believes that someone in the manor will inevitably kill. She often speaks her mind against Protagonist's.
She is the Chapter 1 killer. This ironically makes her theory of someone killing right. Even more ironic considering it was her. She kills Rabbit using Diamond's trap to usurp Diamond's own plan to kill, protecting her from becoming like Valkyrie did. This ends up crushing Rabbit and breaking his ribs, causing him to die of respiratory failure. She is later executed by being hung by a rope.
At the end of the first trial, she reveals her name and identity to everyone because she knows Maid-chan won't. She's Bloody Mary, and her name is Coco Dyer.
- Ambiguously Christian: Subeverted Churchgoing Villain - Valkyrie is not entirely evil despite being a serial killer.
- Angels in Overcoats: Minor case, because she only thinks that she's an angel.
- Badass Longcoat
- Beauty Mark
- Hime Cut: Her hairstyle is an example of this.
- Human Weapon: At the trial, she explains that the day she killed someone in self-defense she became good for nothing other than killing people, and views herself as such.
- Light Feminine and Dark Feminine: Her outfit is much lighter than Diamond's, but they're both very feminine.
- Zettai Ryouiki: Grade A.
???|???Luna's older brother, and King's childhood friend. He seems to be the mature and responsible type, and King refers to him occasionally as his "husband".
- Beauty Mark
- Black Eyes of Evil: Though he's done nothing evil yet, Word of God often hints that Sol's eyes are black for a reason.
- Idiot Hair
- The Gambling Addict
???|???An eccentric young girl who is babied by the rest of the Manor for being the youngest, despite being "14..."?
- Blinding Bangs
- Creepy Child
- Deliberately Cute Child
- I Just Want to Be Normal
- Lonely Doll Girl: Her alias may be Puppet, but she promises that she's not a boring doll!
- Stepford Smiler
???| JabberwockyA boy who wants to be seen as normal more than anything else. He doesn't seem to be good on his own, and is often seen with someone else. Usually Syringe. It's very heavily implied during Chapter One that he's a Serial Killer, which ends up being confirmed during the Chapter Two Trial. His identity is Jabberwocky, who targets abusive parents.
- Adults Are Useless: It's revealed in his chapter one freetime that his parents are chuunibyous that can barely function properly and leave him to do everything.
- Gay Moment: Though any of his moments with Syringe could be read as romantic, Syringe ACTUALLY lifts him bridal style - though Syringe claims it was to prove his strength.
- I Gave My Word: To Syringe.
- You Gotta Have Blue Hair
- I Just Want to Be Normal
Mitsuki Kirigaya| Guardian OgreA boy with a passionate hatred for serial killers, he's one of the brightest minds in the manor. He likes to do his work himself, though keeps an eye on people from afar, though he'll occasionally be seen with Moth. Despite Syringe's hatred for serial killers, he is one. During Chapter Two, he confesses to Protagonist that he is Guardian Ogre, a serial killer noted to only target sexual predators. He considers himself a vigilante, and is redeemable, but it does make him come across as hypocritical.
- Badass Bookworm
- Beauty Mark: Three of them, just like Bled.
- Gay Moment: Though any of his moments with Moth could be read as romantic, he ACTUALLY lifts Moth bridal style - though Syringe claims it was to prove his strength. And he is confirmed to have a crush on Collector after he learns that the other is his detective idol/crush.
- Idiot Hair
- Police are Useless: There's a reason he refuses to turn in King, despite knowing King murdered his sister.
???|???A girl who went through an unknown trauma and became a selective mute. She can't remember the trauma, but the feeling of unease lingers. Despite this, she can communicate easily through text-to-speech on her ID, and is relatively chatty.
- Beauty Mark: Three of them.
- Elective Mute
- The Glorious Warof Sisterly Rivalry: With Flare. She's the smart one.
- Idiot Hair
- Multicolored Hair
- The Protagonist: She's the protag for the most of Chapter 3.
- Repressed Memories: She appears to have these - she can't remember why she became mute, but knows that it was so traumatic for her that she was unable to hear herself speak. She also often gets headaches - especially when certain words are said - like a Trigger Phrase.
- You Gotta Have Blue Hair: Or, blue and red.
???|???A young man who can only be described by others as creepy and overbearing. He's... yeah. To those around him, it's obvious he's a serial killer, and he never denies this - actually outright affirming it, though he yet to reveal which identity is his.
- Beware the Silly Ones
- Breaking the Fourth Wall: Mainly in CH 3, when Maid-chan's out of commission.
- Eyepatch of Power
- Have I Mentioned I Am Heterosexual Today?: Or so he claims. He's actually gay.
- I'm a Humanitarian: He's a cannibalistic serial killer.
- Not-So-Harmless Villain
Umito Ushigoe|???Despite being obsessed with love and horoscopes, Tailor seems not to be extremely unlucky in the area himself. He is a little desperate, though.
- Alliterative Name
- Meaningful Name: Word of God confirmed that it's a reference to the mothy song, Tailor Shop on Enbizaka.
- Stalker with a Crush
- You Gotta Have Blue Hair
Daisuke Hoshizora| Yutsu's Creek KillerA standoffish young man with a foul attitude towards nearly everyone else. However, he's Spring's childhood friend. Or... scratch that. He's Spring's hitman for her yakuza family.
He is the Chapter 1 victim. It is revealed he was killed by Valkyrie, who pulled Diamond's planned trap as a lighting rig with a sword in it crushes Rabbit, and breaks his ribs - some of them puncturing his lungs. He doesn't die instantly, as Protagonist, Spring, and Killer are forced to watch him give out his dying last words. He ultimately dies of respiratory failure.
Maid-chan reveals his name to be Daisuke Hoshizora shortly after his death, but doesn't give his other status. During the first trial, King reveals that Rabbit was Yutsu's Creek Killer.