The minor characters consist of unseen, but relevant characters from the game's backstory.
The Dolphin is a secret character who is not in the mansion but is seen in the paintings and CAT-DOS. He is a surgeon turned Dolphin-y. He lives in a flooded cave somewhere.
The "Romantic" Victim
The "Romantic" Victim is an ill-fated traveler who came to Spooky's house seeking some romance. Quickly becoming hopelessly lost, they started leaving a trail of short journal-like notes as breadcrumbs to document while lamenting their unromantic situation, and also to mark their path so they could figure out whether or not they were just going in circles.
These notes reveal their turmoil as they began to suffer from dehydration, and started to drink the ink they were writing with out of desperation. They later passed out, and woke up to find someone has kindly left them an unlabeled bottle of "red wine". This is predictably implied to be blood. In their last note they find solace in the fact that while they did not find an escape from the manor, it did give them an escape from everything else, and concluded that in the end, their death turned out to be romantic after all.
As revealed in Endless Mode, they had died but hadn't noticed that they were dead, believing that 'I have been granted immortality as a romantic artist' and at the twelfth note Romantic Victim notices they haven't required sustenance in what they assume to be two weeks, and at the thirteenth note they then notice that their skin color has changed to a transparent color. Romantic Victim meets Spooky in the eleventh note and she is upset that they are not doing their job, they boldly state that they have no commander and they go where the wind takes them. Spooky floats into the floor, confused at Romantic Victim's statement, she returns in the final and fourteenth note yet again angry at the Romantic Victim for not doing their job. They yet again deny this, saying that whatever job that they have doesn't sound very romantic, Spooky becomes angrier at them stating that if they don't stop she will take their pen. Apparently, the victim continued to do this causing Spooky to take away the pen, leaving Romantic Victim's fate unknown.
The "Trope-Master" Victim
Another one of the victims of Spooky's house, this character writes notes to fill the role of the "main protagonist" to survive the House, all the while hoping they aren't some "side character." They seem to last a fairly long time, as they notice the monsters are getting stronger and more dangerous as they progress. They conclude that the purpose of the monsters seems to be some form of soul-harvesting and that the monsters effectiveness is based on that. They eventually realize, however, that they lack major protagonist attributes, such as a mentor figure or a send-off from their hometown, and are therefore likely doomed.
The "Chronicler" Victim
The last victim leaving notes in regular rooms, the Chronicler has all their entries specifying the day, starting from the start of their journey. Thanks to this, we can see that they lasted at least a week, but progressively ran out of food and battery life.
Generic Lab assistants
The Generic Lab Assistants apparently work in GL Labs (the manor's laboratory) conducting tests on the various specimens.
In the first Lab's Facility, according to the notes left behind, they ran out of the sedatives needed to keep Specimen 3 (whom they called "Subject 5") docile enough to safely work with. They voiced their concerns to "Spook" about this, only to be laughed at and ignored. Soon after, Specimen 3 inevitably escaped and killed them.
In the second Facility, the player will find out that a team of GL Labs' Assistants has been assigned by Spooky to retrieve something (most likely a loose Specimen), with the tragic aftermath: a member of the team was infected by Specimen 10, followed by the abandonment of the Facility.
Given their position as lab workers, it is possible that Generic Lab Assistants and/or their co-workers created the CAT-DOS computer and wrote its entries.
A female Japanese student who snuck into her class after hours, despite rumors that the school was haunted by a ghost who eats children that do just that.
Unfortunately for Matsuri, these rumors proved to be true, and she was declared missing, having been eaten by the ghost.
A mysterious group of people who performed the vague rituals to appease "The Darkness", as instructed by someone they call "Mother."
An incident involving a girl who was not "pure" occurred, which caused "The Darkness" to consume them. Based on what is hinted at, it is possible that the rituals they performed involved a form of virgin sacrifice, hence the line "the girl wasn't pure". It is also noteworthy that the cult comically denies responsibility for their actions in their writings.
Specimen 5 is somehow involved into this: it could probably be the physical manifestation of "The Darkness" itself, the vengeful spirit of the girl who was sacrificed, or even "Mother".
In the Forest rooms, there are notes written by someone else (very likely a hunter) who mentioned escaping the rooms but then chose to stay there and hunt down the deer for food. They also noted the strange sounds made by them.
The hunter was eventually attacked and was forced to board up the doors of the rooms. Their scattered bones are later seen in a shack, implying they never did escape and were killed by the deer in the end.
The Fastfood Worker
The notes tell the player that the worker was getting a job at this restaurant. Day by day, he started to see paranormal activities happened to the restaurant's clients (in particular, a frequent male customer who "kept ordering the exact same meals for every 10 minutes") and, shortly afterward, to himself, after having eaten the burgers served there. After experiencing too many abnormalities, he decided to quit the job and leave the restaurant for good.
The story in the notes reveals the dark secret behind the unexpected success of the company that had once gone broke. The burgers served at the restaurant were not just normal beef, despite the posters implying "100% beef". It makes whoever slowly ate it falls into deep, disturbing hallucinations ("things that looked wrong", "wailing noises", "brief flashes of a man or animal"), following with a great desire to eat the burgers again and again. However, this "desire" had yet to be observed on the ex-worker, according to the notes.
It is noteworthy that when one of his co-workers reported that the burgers there "smelled like sulfur", the manager "grabbed the kid's neck and shoved his head onto the grill". The employee then "got up and ran out before anyone could do anything", and the ex-worker was told that the employee was fine, but that really shook him/her at that day.
This shows that the company was trying to hide the truth (about the origins of the meat and its effect on humans) from the public eye.
The Phone Gal
Sometimes the player will enter a room with a single desk with a fan and message receiver on top. After a few moments, an unnamed person (dubbed "Phone Person") will talk, saying "Hello" in different tones, and on occasion, tells the player not to look directly at the fan. This could be a trap as if the player stands idle too long, Specimen 9 will appear and attack the player.
This character was apparently studying the mysterious deaths of whales in a particular area. He eventually came to the conclusion that some form of parasite was killing the whales from the inside, but was unable to identify it, until part of his lab was flooded and Specimen 13 killed most of his team. He was the last one left alive, stuck inside a locked off area while the specimen tried to lure him into opening the door.
This character appears in Karamari Hospital. She appears at the end of the game and delivers a message to the player: "You seem different from the others. I've been here so long... I've forgotten so much. This place... It needs to be shut down. I know you can do it, just hurry. You're so close now."
In New Game+, if the player gets the sword and kills all the monsters, the demon child will instead say: "Please don't hurt me! Just leave me alone!"
The Father is a character that appears in Karamari Hospital. He is the writer of a note found at the end of the Ghost Cow maze. Upon reaching the end, the player will find the exit key, along with a note reading:
I'm so sorry my little angel.
I've tried hating the man that took you from us, but in the end the only person I can hate is myself.
You always liked to scare people, especially when they didn't understand something. I was confounded no one understood your costume but I guess people don't read Poe anymore, even with the new Price film. That man clearly overreacted to your fireworks, but we can only blame a PTSD sufferer so much.
This implies that Spooky tried to be scary until the recipient of the prank (a PTSD sufferer) overreacted.
Another secret note written by this character can be found, which reads:
I hate myself for what I am doing, but I can't wait any longer.
Your mother puts on a brave face but I know she wants this too.
I'm making fair progress in bringing you back, but it seems to only work for a moment even with larger thresholds.
Today I think I found the answer. A second device is needed to bind the spirit to the Earth after it has been brought back. I know this sounds macabre but I will turn it off and let you return to Heaven after your mother and I get to see you again.
It is possible that this is Spooky's father who witnessed her demise on Halloween night, as this sequence of events matches up with those that happened in the secret arcade sequence. It also reveals that they tried to bring Spooky back but failed, causing Spooky to become a ghost. This may explain Spooky's unnaturally violent dark side.
Jasper Midnight is a character similar to the Romantic Victim. At first, Jasper thinks the house is just a carnival attraction but is soon driven mad by the monsters lurking in the mansion's depths.
The fate of Jasper Midnight is currently a mystery. If he followed the same fate as the Romantic Victim, it can be assumed that Jasper had died. However, with no remains having been found that can be identified as Jasper's, it is possible that Jasper could still be wandering around until his inevitable demise.
Contrary to most other victims, Jasper seems to enjoy his time in the mansion, despite the Specimens chasing him.
- The Father's note could possibly be talking about the Demon Child, and Spooky programmed the arcade herself to cover up yet another dark secret.
- Interestingly, the death of the "Romantic" Victim is implied to be caused by a mix of dehydration and starvation, despite the many murderous monsters stalking the house.
- The Phone Gal's constant use of "Hello" and "Hi" and the desk with the fan is likely a reference to Five Nights at Freddy's, as it is often joked about that the Phone Guy says "Hello" far too often.
- The Trope-Master avoids picking up the other notes to avoid summoning the "tall man", possibly a reference to either the Slender Man from the Slender Man Mythos or the Tall Man from Trilby's Notes.
- Interestingly enough, the Trope-Master mentions not having a mentor, trial, or a send-off, and is therefore probably not going to make it out alive. However, the main protagonist does not seem to possess any of these qualities either.
- However, Specimen 7 was apparently listed as only being effective on those with psychological trauma. Based on its effectiveness on the player, this implies they possess more qualities than the game lets on.