- Annoying Videogame Helper: Both Pewter and Boss will constantly chime in during each Somnium to remind you how much time you have left and tell you to hurry up. It gets to the point that even Date seems annoyed at how often Pewter reminds him of the 6 minute time limit.
- Ass Pull: A very mild one occers at the Dance Party Ending that you recive at the end of one of the routes. When Hitomi was dancing her right arm was able to MOVE again despite it being rendered unfunctionable after getting shot and destroying the nerves on her shoulder. Probably more for Rule of Funny.
- A more serious one after the first Somnium; it's stated in game that you psync Mizuki both in an attempt to get clues and heal her mute state, and in one route, you succeed the second half of that. The other route, you fail, and Mizuki is sent back to the hospital. The ass pull comes when Mizuki breaks out of the hospital, goes home, texts her teacher, Hitomi, to come spend the night while you're out doing more investigation things... and the very next morning she's no longer mute.
- Awesome Music: Ikume Shrine's theme is a tranquil, moody piece with an underlying melancholy, fitting for the tender moments Date shares with Mizuki and Iris there.
- Complete Monster: Saito Sejima is the Cyclops Killer, the depraved Serial Killer who Kaname Date was hunting for the entire game. The son of Congressman So Sejima, Saito, who had a condition where he only felt pleasure when he's killing, was infamous for causing mayhem but always got away with it due to his father. Starting off by killing animals, Saito eventually grew a tolerance and decide to upgrade to humans, killing Manaka Iwai out of jealousy for taking the attention of his father. Becoming addicted, Saito enlisted the help of Rohan Kamakura to kill numerous women for their morbid obsession, as the Cyclops Killer. When Falco started to suspect the duo for the murders, he tried to get evidence from them by swapping bodies with Rohan and trying to gain decisive evidence from Saito. However Saito caught on and swap bodies with Falco out of curiosity after learning about Psyncing from him. Trapped in Rohan's body with amnesia, Saito later recovered his memories and wished to return to his original body and get revenge on Falco. Now resurfacing as the New Cyclops Killer, he killed numerous friends and associates of Falco by swapping bodies with them and then killing them, while taking their right eye. He'd kill anyone for his goals, including his father. In the true ending, Saito manages to get his body back and captured Falco's love ones, with the intent of killing them in front of him. A complete and utter psychopath, Saito took many lives for his own self-indulgence and need for vengeance.
- Ensemble Dark Horse:
- Kagami for being a Running Gag character and his surprisingly positive relationship with Date, in spite of being the butt of his jokes. You'll find quite a lot of people expressing their happiness over the fact that he was included in the dance at the end.
- Mama for being a positive representation of LGBT community, being Date's informant, as well as her her ship with another fan favorite, Moma Kumakura.
- Mayumi Matsushita. Many fans admit that they initially believed Mayumi would be a character they'd care the least about, as a result of her cartoony design and her initial attitude towards Iris. Cue Ota's route and her Somnium, PSYNCIN' IN THE SUSTaiN, and she became one of the fan favorites. Reasons include her being a supportive mother and her Somnium showing Tear Jerker and Heartwarming Moments of her life with dementia.
- Fan-Preferred Couple: Judging by the fanfiction, a lot of fans ship Date with Hitomi. It does help that the story teases the two of them being interested in each other as well.
- Friendly Fandoms:
- Zero Escape, unsurprisingly, considering both games are by Kotaro Uchikoshi from Spike Chunsoft. If you liked one game, chances are you're going to like the other. Even certain game mechanics are the same, such as unlocking certain routes only after completing other accessible ones.
- Danganronpa, once more without a surprise, considering both games are mystery genre games by Spike Chunsoft.
- He Really Can Act: Allegra Clark does a great job as the calm and collected Boss, but she really gets to show off her acting range when she plays Saito inhabiting Boss's body, almost going full Hannibal Lecter in his mannerisms and overall speaking structure. The way she just quickly flips from normal to unhinged in the span of a few lines of dialogue is somehow one of the scariest moments in a game already filled with frightening, nasty moments.
- The switch of Saito in Date's body and Date in Saito's body takes the cake. DC Douglas and Greg Chun essentially switch roles, and manage to, despite still sounding like their 'bodies' voices switch personalities completely. Greg Chun goes from a goofy but well-meaning perv in Date to a complete psycho in Saito, and he absolutely sells it, while DC Douglas does the opposite and sells it too.
- Iron Woobie: Hitomi Sagan. The poor woman just can't take the break. She loses her two best friends from high school, one of which she witnessed being killed at a young age. She took care of her daughter and treated her as her own daughter. Said girl was diognosed with a maladaptive brain tumor, only curable through an expensive nanotechnology; and who died as a result of not having it treated on time or being killed by a serial killer in most of the routes. Hitomi's love interest suddenly disappeared with no explanation. When she got to meet him next time, she had to visit him in jail, and there he claimed to be someone else in her lover's body. She was also shot in her right arm by the person she loved (although accidentally while trying to protect her), resulting in her not being able to move it (aside from the dance at the end).
- Nightmare Fuel: The Psync during the Resolution Route, when Saito Sejima systematically goes through Date's Somnium, breaking his Mental Locks to pull a Grand Theft Me back into his original body. Just the thought of someone pulling this Mind Rape on you is chilling to some.
- Ships That Pass in the Night: Mama and Moma have only been shown dancing together for a brief moment (and have similar names), but this doesn't stop them from being shipped by the fans.
- Squick: The culprit Saito Sejima, claims during the Annihilation Route that he disposed of his previous body's eyes by swallowing them (backed up by Shoko's turning up in Renju's body after Ota Route). This means Boss' body had So's eye in it, and worse, that Date unknowingly has Renju's eye in his gut during the True End.
YMMV / AI: The Somnium Files