Take your standard overpowered protagonist isekai formula, set it in a Cosmic Horror Story, have your protagonist be the biggest and most dreadful horror of them all, and you've got Instant Death.
- Yogiri. He possesses the ability to kill his targets instantly just by having the intention to do so. Even if you were to stay out of his sights, that power can also detect any form of hostility and would retaliate appropriately. It didn't help that he looks like a Ridiculously Average Guy at a glance, making it a nasty surprise for his enemies.
- As the story gradually reveals information about Yogiri, the audience learns he's not just a human with a weird ability but an Eldritch Abomination taking on the form of a boy. And one of the Sages, Aoi takes a glimpse into Yogiri's true powers and discovers to her horror that he's actually THE END. Not metaphorically. Not rhetorically. Not poetically. Not theoretically. Yogiri's just THE END. STRAIGHT. UP!
- Visually, "The End" is represented as an endless, all-devouring void of nothingness with countless unblinking eyes, covering all times and places throughout all of existence. Trying to challenge, resist or escape from such a thing is seen as the absolute height of hubris and idiocy in the series, and it simply revealing its presence is enough to break an unfortunate soul's mind beyond repair.
- Calling Yogiri's power Instant Death is a massive understatement as its true ability is to permanently erase the target's essence of being, meaning not even resurrection or time manipulation can bring them back.
- Child Yogiri
◊ is Played for Horror more than perhaps any other entity in the whole series. Unlike the older Yogiri we follow through most of the series who at least has some self-imposed rules so he doesn't end people willy-nilly, his younger self was more than happy to kill droves of people just for getting in the way of his objective or disobeying him, whether or not they actually tried to harm him. - The organization responsible for him kept him locked up in a highly-secured underground facility for the safety of the world. However, a young Yogiri revealed to them one day that they never had him contained at all. He just never had any reason to leave the facility until his beloved caretaker was kidnapped and he killed anyone that got between him and her.
- At one point, Sion summons an employee of the Institute tasked with tracking Yogiri's movements in order to gain more information about him. Said employee rants semi-coherently about the crisis Yogiri's existence presents to any world he's apart of and how he lives in fear of his every movement, all of which is cut short by the employee having his head procedurally detonated as he begs to be saved. Seemingly the reason for this is that he was in the same universe as Yogiri while his first seal was unlocked, and he'd been exposed to Yogiri before. Even Sion, who has no problem vaporizing people at a whim, was put into momentary Stunned Silence at this sight.
- As the story gradually reveals information about Yogiri, the audience learns he's not just a human with a weird ability but an Eldritch Abomination taking on the form of a boy. And one of the Sages, Aoi takes a glimpse into Yogiri's true powers and discovers to her horror that he's actually THE END. Not metaphorically. Not rhetorically. Not poetically. Not theoretically. Yogiri's just THE END. STRAIGHT. UP!
- The Sages are a group of magic users that are either power hungry or determined to protect their world even if it means causing millions of casualties to do so. And how do they replenish their numbers? They summon people from other worlds and implant them with their Gifts, turning them into Sages as well. Thanks to the powers granted by the Gifts/Battle Songs, they treat the world like it's a videogame, with them being very light on the idea of killing.
- One such summon, Yuuki Tachibana has the ability to control people and under the influence of the Gift, he slaughters villages and enslaves any woman he fancies into his harem. This part of personality is omitted in the anime adaptation though.
- The Battle Song system in particular needs special emphasis. While it’s clearly meant to be a take on the LitRPG systems and powers so common in other Isekai stories, it’s a much darker take on the idea. Yes, it can grant you power and bring out any abilities or talents you have hidden potential for. However, the system alters the user’s mind, making them more amoral and willing to kill, to the point where a user will gladly leave their friend behind as monster bait. The system can be installed in someone without their consent, is subject to various areas and skills that suppress it or defend against it, and, most terrifying, can be used as a kill switch if the user tries to go against the person who gave it to them (such as the Sages), or just be used to kill the user if said Sage is bored.
- The World Eater, as his names implies, is an Eldritch Abomination that devours entire universes. However, over time he grows bored and creates human constructs to mingle with the populace. His first construct lived as a humble man and started a family but he didn't like that so he created a new identity where he became a vicious tyrant that goes about destroying any settlements.
- Really, despite the setting could be the dream of an action/rpg gamer, the entire setting is Nightmare Fuel for an average person. Befitting the kind of world most action and RPG game could be, the entire world is full of horrendously sadistic beings who are drunk on their own power, and casually murder/enslave/torture everyone who even looks at them funny or doesn’t bow down to them. And the average person doesn’t have any way of going against it, especially since those sorts of people are the ones who literally run the world. As if that wasn’t enough, there are beings that exist outside reality (such as the World Eater and other Cosmic Horror Story Eldritch Abominations), or gods so powerful they can wipe out entire universes with less effort than twitching a muscle. Frankly, the only way you have a guaranteed chance of survival is to have power/ability comparable to those sorts of beings….or be Yogiri.
- And that's just for the ones living in the "fantasy world". People from a "real world" can be pulled in to the "fantasy world" in a whim. Not to mention the "real world" also has its sorts of supernatural beings as well, necessitating a supernatural institute to contain them.
- In Volume 4, Sion shows that for all her attractive appearance and personality, she is still a psychopath.
- The Sage candidates are not safe from her as proven when Sion commences a battle-royale style fight each other until one survives and becoming the new Sage.
- Sion then said that the alternative is for the Sage candidates to kill herself. When Fukai chooses to stand up to her and tries to kill her with his Shinigami powers, Sion decides to humor him for a bit before revealing to his face that every time he does it, she's leveling up every millisecond. She spends a short while to see Fukai completely sweating in terror and then proceeds to blow his head off with a punch (in the manga) or a Finger Poke of Doom (in the anime).
- Yukimasa's fate is flat-out disturbing. Using his book to find ways to kill Yogiri, it results in him finding out he's already dead. As Yukimasa tries to undo it, he grows from annoyed to being completely terrified. Out of desperation, he rips out all the pages of the book despite losing his powers as consequence...And the pages stick to the ceilings, floors and walls to repeat the outcome in Yukimasa's face.
- Then there's the part when Sion finally confronts Yogiri and it's not pleasant....for HER. She intends to catch him off guard but Yogiri simply destroys her body parts bit by bit. Sion finally realizes the threat Yogiri poses and flees back to her manor only to learn to her horror that Yogiri isn't done with her and continues the Cold-Blooded Torture, including her assistant and implied lover Youichi. At this time Sion gaves up and give a piece of Philosopher's Stone, the source of her Sage powers. Without context, the scene can be easily interpreted as Yogiri being the evil there.
