Akita's death, and even the sequence leading up to it, is loaded with fridge...
For example, the amount of times that Akita has been stabbed is twenty-one times, the amount of student taking part of the Killing Game.
Ayano's dream at the beginning of her narration with Kazuhiko is almost word to word the same one Akita has with Mitsuru and Hideyoshi. This is to show that Kazuhiko is both Ayano's love interest, being her boyfriend in canon, and a future killer.
Extra fridge that this also foreshadows Ayano being somehow related to Akita, along with Izumi.
More fridge. This was before the audience knew of Akita's death and foreshadows it with Ayano being the new protagonist.
Near the end of the prologue, Akiza has her first line as puhuhuhu. Since she was not introduced into the story yet, everybody assumed that it was just Monokuma. This counts as foreshadowing about Akita's alters and her past related to despair.
Ayano's talent being hacking. Not only is she good with computers, she also hacks into the role of narrator!
Why do Ayano and Kazuhiko blush whenever people call them Aya and Kazu, which are supposed to be one of their nicknames for each other? They're sex names!
Probably nicknames but this still counts. Although it is canon that Ayano and Kazuhiko are sexually active (and both adults), there's no evidence that these are sex names. Most likely they're embarrassing nicknames.
Kazuhiko's execution. Like all the other executions in the series, it is covered in fridge and explores parts of his character that will be more explored later in the story.
The first part with the conveyor belt mirrors Detention. Like Kyoko and Matoko, Kazuhiko's trial is rushed since it would reveal the truth of the Killing Game. It continues unlike Detention because Kazuhiko really did kill Akita.
Also, it could show how, like Matoko, Kazuhiko is somebody who believes in hope and will do anything for his best friend, Ayano. They can be foils of each other.
The second part of the execution is similar to Akita's unofficial one revealed in the extra content. This is because Kazuhiko killed Akita and is the one that knew what was happening to her the most.
Kazuhiko loves attention and is described to be like a puppy. What do the Monokumas do? Throw rocks at him. Kazuhiko wants people to praise him, but he gets booed while he painfully dies.
Also, Kazuhiko does not die in a flashy way. Kazuhiko succumbs to his injuries and that's it. Even though he believed that he could spread hope and be important to the world, Kazuhiko just became another body in the death count.
Even though Monokuma allowed Fuyuhiko to join into Peko's execution, he probably did that because there was a chance of survival. Monokuma in this game is much more cautious and wants people to fall into despair. He most likely brought Ayano out of there because she would die, not because she would get in the way, which will cause him to break one of his rules.
Akita's unused execution is also filled to the brim with fridge and reveals more about her character and the other people inside of her head.
Of course, the arena being a circus is not only a shoutout to Monokuma Theatre, but her true talent of Ultimate Ringleader. It also reveals the turmoil inside of her head since on the surface circuses are friendly, yet some are known to be quite cruel and have a lot of secrets.
The constant spinning and multiple people appearing can relate to Akita's crisis. She doesn't know who she is, and, even when faced with evidence, claims that she is a mediator, not a ringleader.
There are dolls all around her because that is how she is viewed by the Committee and she knows it. She is literally another doll to them and setting her on fire changes nothing.
In the prologue, Mirabilis was only able to 'purify' one student: Akita Yamazaki, which involved hitting her in the head with her wand. She was also shown to have hit Kazuhiko in the head with her wand in the prologue. Later, in chapter one, Akita was the victim, and her murderer was revealed to have been Kazuhiko, who was executed for his crime. Akita and Kazuhiko were Marked to Die by Mirabilis, being the only characters she successfully hit with her wand in the prologue and first chapter. They were even hit in the order they died.
Note that there were originally twenty-five students in this project. There are six people in the class that were supposed to be in the game but did not arrive at the school on time. With Akita not being an Ultimate, and the mastermind from the first class, there were actually twenty-five students!
Ayano's Nishiki nightmare of her execution is exactly like all the other executions even though it is not real. With the Monokuma Theatre being canon and plot important in this book, we can assume that this is her actual execution.
Like in the Killing Game, and her backstory beforehand, Ayano cannot escape her situation, no matter how hard she tries. She may always get close, but she herself pushes herself back, whether it be her depression or love of Kazuhiko.
Ayano tries to make herself die another way than finish the execution, much like Kaito Momota. But she's unable to because of the demons from her past, the most likely symbolism of the clicker, always grabs onto her.
She is literally put into the trash bin by Monokuma. Monokuma views her as nothing more than trash.
Much like Mukuro from the first game, Ayano gets speared to death. Because she has broken the rules before (she broke the floor, but Monokuma lets it slide to torture her later), she should've been punished like Mukuro. Also helps that she is Izuru's child, a former member of the Ultimate Despair.
Why is Shinichi so short? Because he was starved by his mother! This is also why it does not take that long for the nightshade to kill him compared to other cases since he has the figure and weight of a child. Not to mention he was already stressed out, was surrounded by people that didn't know and were freaking out, and ended up throwing up. Throwing up is a rare symptom of nightshade poison and is to be avoided, but the students didn't know that, and Shinichi ended up choking on his own vomit.
Kira's fake execution is, yet again, filled with fridge.
Something about her suicide plan. Note that Kira isn't that much taller or heavier than Shinichi, so it would've had the same effects. Kira wanted something that would probably kill her quickly but give her enough time to confess to all of her classmates. She might have even felt guilty about helping Ayano Kirigiri, and, much like Nagito before her, gave herself a painful death to help right her wrongs.
The symbolism of the hand. Kira starts her fake execution trying to break free from it, but, once she does, breaks her leg and begins to run as fast as she could from it. The hand could symbolize her relationship with Kirigiri and not being able to run from her grasps.
Kira is also surrounded by diamonds in the oven she is forced into. Not only does this hint at the process of making jewelry, which she is one of the Ultimate Jewelers, but she is surrounded by people that shine brighter than her. Since we do not know who is the true Ultimate Jeweler, her or Cassius, this could symbolize that. Kira also seems to not think to highly of herself, viewing herself as lower than others, which is why she decided to try to kill herself to help her classmates, so she is just normal while everybody around her are diamonds.
Cassius's execution. Note that both Kira and Cassius have references to diamonds in their execution titles (Diamonds are a Girl's Best, Worst Friend for Kira, while Cassius is Cassius's Killing Adventure: Diamond is Breakable), which shows their relation to each other, as both people had a lot of Ship Tease and both being the Ultimate Jeweler.
Cassius's execution has references to the three second chapter executions beforehand, Mondo, Peko, and Kirumi. They all have sympathetic motives, much like Kira and Cassius. Kira wanted to give everybody free access to water, while Cassius did not know he was murdering anyone and just wanted to protect a secret, much like the three other second murderers.
Cassius's execution is how diamonds are made. This is because Cassius thought of himself as higher than the other characters due to his noble blood and pride. He is like a diamond that shines brighter than everything else, but diamonds are actually worthless. He is thrown in the acid by Monokuma like he is a piece of trash.
The reason why Kira was allowed to try to interfere with the execution and Ayano wasn't is because it is her punishment. Note that the header says time for punishment for Kira and execution for Cassius. Since she tried to kill herself and accidentally caused Shinichi's death, Monokuma wants to punish her.
Note that Kira gets blinded by Cassius at the end of the execution. Not only did she try to save him in a blind fit of pure emotion, she is also blinded by her mixed loyalty to the Committee and Kirigiri.
Monokuma calls Yasu Yumiko before punishing them in the torture room. Since Yasu is nonbinary, it is probably safe to assume that this is Yasu's dead name.
Note that Kotori states that the subjects of Personality Experiment #045 should not be exposed to head trauma except under a controlled setting since the side effects are unknown. Now keep in mind that one of these experiments is highly hinted to be Akita Yamazaki. When do the voices first show up? When she's exposed to head trauma. No wonder she experiences Sanity Slippage!
First the mastermind knocked Akita out so she could be part of the Killing Game. Note how the text mentions that the mastermind hit something over her head, enough to knock her out.
Second is Mirabilis's purification. Purification involves hitting somebody in the head with a heavy wand.
It's time for yet another execution! This time for Takayuki Anno, the Ultimate Private Investigator, and Hideyoshi Yamazaki, the Ultimate Clown.
The most obvious is the Jekyll and Hyde reference. Though what is unique here is that Takayuki and Hideyoshi both fit Jekyll and Hyde. While Hideyoshi acts like Hyde, he is the original personality like Jekyll. Takayuki is the opposite. The execution even has subtle references to the story (such as the needles).
Hideyoshi has the first part of the execution dedicated to him. It mirrors Akita's execution due to the two of them mirroring each other in the story.
The Monokumas in the morgue could symbolize all of Hideyoshi's victims since it is heavily implied that Hideyoshi still killed people when he shared his body with Takayuki. Hideyoshi would go out and murder the victims, while Takayuki would figure out who did it and try to bring him to justice, not realizing he is the true culprit.
Takayuki is killed just like Mirabilis, shot in the head. This is because Hideyoshi is the person who debatably caused her death. He was also being punished for Mirabilis.
Mirabilis was punished via choking rather than being torn apart. Why? So she couldn't tell the others anything before she died!
Namita's executions. Oh dear lord. There are so many fridge moments to be found in both of them that it hurts.
Note that both of the executions are game themed. Note how Namita has a persona much like a lot of players in these games, and how she is forced into the killing game. It's exactly the same in this situation. Forced into a game, but now forced away from the persona. Now that she doesn't have the persona, Namita fails miserably. Whenever things don't go her way, Namita really doesn't act like the leader that she most often is acting as.
Also something about the executions: their names. Hope edition and despair edition. For hope, its where the students have hope and try to escape and the execution is liveable although painful. But, for despair, the protagonist has been forced into that state of mind, the students' morale is at an all-time low, and there's no chance for Namita to survive. Clever.
Namita is forced onto some sort of twisted slide game for her first execution. They are all of the different obstacles she has to overcome. These can be connected to her psyche as well. The first is filled with blood and saws, referencing to how Namita has become a killer (and also possibly hinting to her possible amoral actions destroying the lives of people in her parties for more press coverage). Oil can be how Namita's past actions about her parties can be seen as slimy. The third is all loopy as it reflects Namita's twisted morals. Although Namita is a good person, she has done horrible things. Meanwhile, the side looks fun but is really quite dangerous. The fourth is an old slide that breaks away instantly, like Namita's sanity when Kaneshiro messes with her and Miyuki. Being the most clever, however, is the normal one. It's literally normal until it reaches the end, a dark abyss. An accurate description of the lives of those who Kaneshiro tortures, much like Namita.
Note why Monokuma probably changed Namita's execution. Other than the despair, Namita is shown not to be that good at adapting quickly. So what does Monokuma do? Force her into a situation to react quickly. This is probably why the game isn't clear to Namita as well. Because Namita cannot think on her feet except if she's in control. And she's clearly not in control.
Why does Namita get stabbed in the heart? Because her heart was broken by her very own actions. Ouch.
Like Junko with Matsuda, Miyuki and whoever else killed Namita stabbed her long after her death until she was unrecognizable. Like with Junko, Miyuki was Namita's lover and in despair.
Remember back when Ayano was sexually assaulted by the fake Kazuhiko? Kaneshiro probably did this to see what gave her a reaction to despair.
Please note how similar the sexual assault scene with the fake Kazuhiko is to the rape scene with Kaneshiro. They even both take place in a hospital! Kaneshiro really was just testing Ayano! Hotaru probably saved her from a worse fate back when she was dealing with the fake Kazuhiko.
Ayano is stated to not like babies. What did Kaneshiro do while driving her into despair? Show her a photo of a dead baby.
Why does Monokuma kill Minato? Think about all of Minato's actions. Minato has shown to be resistant to despair and help others with despair, including one of Kaneshiro's obsessions, Akita. Not only is Monokuma teaching the students a lesson, Monokuma is destroying a chess piece that he has no control over.