Each night, I went to sleep wishing that this would turn out to be a nightmare. Yet each morning I awoke to find that the world was just as horribly warped as it was the day before. I have to live while blending in, while acting like one of them. Just as I've done these past three months, I will continue to do for the rest of my life.
A Visual Novel / H-Game by Nitro+, Saya no Uta ("Song of Saya") revolves around a medical school student, Fuminori Sakisaka. Before the main plot, he was involved in a car accident which killed both his parents. He was saved, however, by an experimental brain surgery... which just happened to drastically alter his perception of the world. Everything now appears to him as if it were made from guts, slime, and gore.Well, almost everything.One night while still in the hospital, a girl dressed in white appears before him. To him she appears completely normal, and above that, downright beautiful. Rather than consider the why of this, he latches onto her as his reason to keep living, and convinces her to move in with him once he's released from the hospital.The more things go on, however, the more Fuminori withdraws from the rest of his life. His friends become increasingly worried for his sake, including Yoh Tsukuba, who has had a crush on him since before the accident. His doctor, Ryoko Tanbo, still has the impression that there's something he's not telling her... This is true enough; out of fear of becoming a lab experiment, Fuminori never told her (or anyone save Saya) about the way he now sees the world. Finally, there is his search for information on Professor Ougai. All these things and the decision on whether Fuminori wants to be normal interact to drive the plot forward.
Adult Fear: Pretty much all characters in the Visual Novel meet horrible endings, but for this trope in particular, Yousuke is the primary example and arguably the only one worthy of feeling sorry for. A doting family man has his life suddenly thrown into hell after Saya gives him a "new" way to see things, from there on the otherwise upstanding citizen goes apeshit insane brutaly killing his wife and daughter out of pure horror everything in the world has become in his mind, and even enjoys it in a very twisted way, and as if this wasn't excruciating painful enough Yousuke's mind deranges so much that after he meets Saya again, with she now being the only person he can see in human form, the first thing in his agenda is to viciously rape her. A true nightmare - no, better yet - a night terror to any decent family man out there.
Adaptation Decay: The American comic book of Saya no Uta takes some... "creative" directions with the plot. Fuminori is changed to a more "American" name (Josh), Saya is no longer Cthulhu, but rather the result of secret government experiments. We are shown Saya's true form at the end of the first comic, despite never actually seeing it in the original story— which is arguably scarier than actually knowing. Saya is also "aged up" to a less controversial body in Josh's eyes. While she was almost a child in the H-game, she's now about 18 physically.
Black Speech: Fuminori's hearing sense, along with all his other senses, is also warped: all voices but Saya's sound to him distorted, with weird frequency changes and other sounds hard to describe. This visual novel is dubbed, so we sometimes get to hear those voices as he hears them.
A different example we can also hear, later in the story: when Oumi breaks into Fuminori house, how do you think she hears Saya's "Welcome home!"
Body Horror: Happens to Yoh when Saya transforms her into the same being as herself. Then in one of the endings to everyone in the world.
Broke Your Arm Punching Out Cthulhu: In one ending, Dr. Tanbo & Kouji manage to kill Saya and Fuminori subsequently commits suicide after delivering a mortal blow to Tanbo. Kouji, the sole survivor, becomes a paranoid schizophrenic cross between Tanbo & Fuminori, knowing he's permanently psychologically damaged from what he's witnessed, spends the rest of his life with a revolver with one bullet hidden in his bathroom, in case he ever reaches the point he can no longer stand live with the insanity and kills himself.
Coitus Uninterruptus: While Fuminori is on the phone, being threatened by Kouji, he's shown to be forcing Yoh to give him a blowjob the entire time, and he segues into a conversation with Saya right afterward.
Color-Coded for Your Convenience: In Fuminori's mind, red represents gruesome, disgusting and bad, while green represents ethereal, calming and good. For example, the gory world is primarily red in color, while Saya's hair and eyes have an ethereal, greenish tint.
Cthulhu Mythos: A heavy influence on the story, and Saya's background. It shows.
Despair Event Horizon: The result of one ending. Dr. Tanbo is left to watch the world as the human race is steadily converted into the same grotesque beings as Saya, knowing the same will happen to her in time. She takes is surprisingly well, which is to that say she accepts it at all.
Most prominently is Yoh being turned into the same lifeform as Saya - an agonizing procedure that takes twenty hours to complete - and becomes the pet of the Sakisaka household. Fuminori is simply glad that now he doesn't have to go out of his way to kill Yoh.
Fuminori in ending 1, where he's locked away in a sanitarium, probably for the rest of his life, and will likely never see Saya again as the two say goodbye forever using text messages on a cell phone passed back and forth underneath his cell door.
Speaking about Fuminori, his point of view alone will drive you insane and if he never met Saya he would have committed suicide a long time ago.
Dr. Tanbo in ending 2, where Saya "blooms" and every human in the planet changes into her type of life form, but Dr. Tanbo, being high up in the mountains where the spores have trouble reaching, transforms agonizingly slowly over the course of weeks as she completes transcribing Dr. Ougai's research on Saya for her own personal pride. At one point she even chops off one of her arms that had undergone the transformation while the rest of her was still human.
And finally, Kouji in ending 3, as the only survivor of the Final Battle and last person remaining with knowledge of the now-deceased Saya's true nature and Things Man Was Not Meant to Know has to live knowing he can't talk with anyone about what he's witnessed lest they think he's crazy (which he partially is at this point and likely getting worse), his girlfriend and two best friends dead, and a revolver loaded with one bullet hidden in his bathroom in case the day ever comes he can't take his schizophrenia and hallucinations anymore and commits suicide.
Huge Guy, Tiny Girl: Fuminori and Saya. This may not actually be the case with Saya's true form (though she is apparently small enough to fit under Yousuke's couch), but her human guise is freaking tiny either way. (This could owe to the art style, however.)
I Cannot Self-Terminate: That moment in the abandoned nut house where Yoh, feeling immense and constant pain as a side effect of her transformation, begs Kouji to kill her.
Kill 'em All: The latter two endings, one in which Saya "blooms" and her spores transform every human on the planet into what she is, and the other ending where every remaining major character except Kouji dies in the Final Battle and even then he is Driven to Suicide.
Not Quite The Right Thing: The game's first branching off point is the option whether or not Fuminori wants Saya to fix the broken part of his brain and go back to seeing, hearing, feeling, and tasting things as he did before. Accepting her offer gets him thrown in a sanitarium for the murders of Oumi & his neighbors as he and Saya say their goodbyes and he spends the rest of his days waiting for her to return as she sets out to find her missing father. Refusing her offer causes Fuminori to leapfrog the Moral Event Horizon into Villain Protagonist territory, by engaging in cannibalism, rape, and murder for the rest of the game. Ironically, while the acceptance ending is objectively the happiest ending with the fewest number of people dying it's almost treated as a Non-Standard Game Over.
Pixellation: Par for the course for a Japanese H-game. The player is given the option to censor some of the worst parts via a filter before the game starts.
Police Are Useless: The reason given by Ryoko for not calling police (beside her own crimes).
Psychopathic Manchild: Saya. After being raped, she degrades into The Sociopath, although Fuminori's cheerfully skipping across the Moral Event Horizon probably doesn't give her any incentive not to. A bit of Fridge Brilliance when considering Saya only had long-term human interaction with Fuminori and mad scientist Professor Ougai, neither of whom is exactly sane or normal, meaning Saya never learned of normal human behaviour or morality.
Pyrrhic Victory: In one ending, Dr. Tanbo and Kouji manage to kill Saya and Fuminori. However, Dr. Tanbo dies, and Kouji ends up schizophrenic with constant nightmares and is eventually Driven to Suicide.
Rape as Drama: Happens to Saya and Yoh, though both get over it fairly quickly.
...As long as you consider becoming a mindless sex doll "getting over it", in Yoh's case.
Rasputinian Death: Certain precautions have to be taken in order to kill Saya, or else she'll shrug off the damage.
Room Full of Crazy: The room where Ougai is found. The painted rooms in Fuminori's house might count, too.
Sanity Slippage: Anyone who sees Saya's true form or is suddenly exposed to the "guroverse" is prone to at least some, if they don't snap immediately. Saya also has some subtle Sanity Slippage after she's raped.
The Unreveal: All you ever see of Saya's true form is a few heavily shadowed tentacles.
Averted in the comic adaptation, where the final image of the first issue is Saya having sex with Fuminori Josh — in her true form, as seen in a mirror. It's every bit as disturbing as you'd imagine. We get to see her true form again in the final issue.
What Measure Is a Non-Human?: None of the humans have any problem with killing any of the aliens because of how freakishly inhuman they look. Fuminori even says that it's easier for him to kill people when he sees them as flesh-monsters, through his warped perspective, than as actual human beings.