The story expands on the songs of the Original Sin Story Act 1 album, primarily "Project 'Ma'," "Escape of the Witch, Salmhofer," and "Moonlit Bear". In the Magic Kingdom Levianta, before the creation of the Seven Deadly Sins, the queen Prophet Alice Merry-Go-Round was forced to give up her twin children by the senate, children whom she claimed were meant to be the vessels for the dragon god, LeviaBehemo. Now she prophesies that the senate must pay for their mistake, and artificially recreate the "Twins of God" by selecting a virgin witch to carry them to term. And so Project 'Ma' begins, amidst a backdrop of political intrigue and those who want to use the project for their own ends, among them the vengeful long-lost son of the queen, Adam Moonlit.
The story covers the disastrous first and second Projects and their aftermath, expanding on the world of Evillious before the Levianta Catastrophe completely changed the cultural landscape of the region. It is to be followed by Original Sin Story: Punishment.
The novel provides examples of:
- But He Sounds Handsome: Horus notes that Seth is the most brilliant out of all of his apprentices. It's revealed in the next chapter that Seth is Horus.
- Darker and Edgier: While mothy is no stranger to dark subject matter, this book is nonetheless significantly grimmer than other entries in the series. Among other things, it features an (unwittingly) incestuous pairing being played for drama (and this time the relationship takes up much more of the book,) a gruesome miscarriage as a plot point, one character being repeatedly raped in her backstory, and has a bleak tone overall, with less levity than in previous works.
- Dramatic Irony:
- During the ritual to make herself into 'Ma', Eve sees a vision of two children coming home and believes they are her children, becoming excited to meet them. Fans who have read the rest of the series know that they are Hansel and Gretel, who end up murdering her and Adam.
- Adam spends the rest of his relationship with Eve believing her love for him is because of the Venom he gave her, whereas Seth reveals in his chapter that the Venom had no effect on her. There's also how neither of them know they're twins, something the audience learns halfway through the story.
- Despair Event Horizon: Eve crosses it when the children she'd placed her hopes and dreams on are born as stillbirths, implied to be horribly deformed at that. She's driven insane and spends the rest of the novel in a state of denial, and is even catatonic for a while afterwards.
- I Will Only Slow You Down: When Meta is making her escape with the children, Pale tries to come along with her, but the four of them are caught in sleeping gas; although Meta and the twins are unaffected, it starts putting Pale to sleep. He insists she go on without him, since he knows he's too useful for Seth to just kill.
- Laser-Guided Amnesia: Seth forces Pale, who had been trying to kill him, to be "reset", and uses that loss of memories to give him an entirely new identity as Kiril Clockworker.
- Paper-Thin Disguise: Seth Twiright is noted as looking identical to Horus Soltnse, the previous head of the research institute, except younger. The chapter from his perspective reveals that he knew it would be a better idea to change his looks, but he just liked them too much.
- Rapid Aging: The body Seth uses during his Horus identity is inferior to that of normal humans and ages too fast, leading him to discard it later. This defect carried on to Pale's body as well; though he staved it off for a while, Seth ends up transferring him into a new body.
- Adam and Eve's ages are both moved up to being around twenty when the first project began, and similarly Meta, who was at first noted as being around Adam's age, is made younger than Eve.
- The woman that Meta encounters in "Escape of the Witch, Salmhofer" isn't Eve as depicted in the song's music video, but is instead a woman from one of the villages Apocalypse attacks.
- Eve in the song "Moonlit Bear" realizes the truth of what she'd done once Adam talked her down and was subsequently horrified by it; in the novel, she comes to understand that the fruits are really children but still doesn't fully comprehend what happened, instead thinking they're her children.
- The Reveal: A few surprising ones are given in this one; Adam and Eve are twins, Eve is a Levia inheritor and as such the Venom drug actually had no effect on her and Pale Noel and Kiril Clockworker are the same person.
- Start of Darkness: This book demonstrates how Eve starts as a heroic and well-intentioned witch who hoped to help reform the corruption in Levianta, and ends as a shell of her former self who will eventually become the Demon of Sloth the audience sees in the Gift novel.
- Surprise Incest: Adam and Eve, the infamous Star-Crossed Lovers of Evillious, are revealed to be twins who were separated at birth. This is earlier alluded to as them feeling as though they know each other already when they meet, though unfortunately they misinterpret their feelings romantically. Their being related (with Adam secretly mixing his own genetic material into the God Seed) is directly responsible for Eve's failure to carry Cain and Abel to term.