Isekai'd as a side character

“The Birth of a Hero” was a novel focused on the adventures of the main character, Choi Han, a high school boy who was transported to a different dimension from Earth, along with the birth of the numerous heroes of the continent. Choi is reincarnated as an insignificant early villain killed in order to help develop the protagonist’s character. He has no intention of just sitting around and waiting to die.
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An unlucky past life. When I opened my eyes after dying, I got not just a golden spoon, but a diamond spoon. Finally, the flower road in my life has bloomed. However, I’m adopted? Furthermore, this is the world inside of a novel. I’m destined to be murdered by my psychopath younger brother.
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○ : pseudo-incest; kidnapping

After Seo Yuri gets into a car accident during a trip back home, she reincarnates into the novel, “The Song of the Moon,” and becomes the elder twin sister of a side character who meets a destructive ending—Selena. Selena hopes to prevent the destruction of her family, however, she is forced to take the place of her runaway brother, Celestine, in the knights squadron. Will she be able to avoid the villainous Crown Prince, Ignis, and survive?
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An ordinary graduate student reincarnated in the the novel “Eternal Love”, written by her at the age of 15. However, instead of arriving when the original story began, she reincarnated seven years in the past.
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○ : pseudo-incest; child abuse (not really seen)
○ She was supposed to die originally but didn’t, yet she seems convinced that she is destined to die anyway

After what seemed like ages of waiting for the story to begin, Ainéis finally meets Tego Literuon, the main character of the fantasy novel she woke up in eight years ago. The only issue? Due to the novel's description, she thinks that Tego is secretly a woman in disguise.
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I accidentally took possession of someone in a 19+ reverse harem novel. The problem is that I became Roxana Agriche, the older sister of the sub-villain. My damn father kidnapped the heroine’s brother. Now, is the only thing left to meet a terrible end from the vengeance of the heroine? But what if I can avoid that horrible development?
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○ : violence; torture; mutilation; incest (one-sided, side character)

The villain was reincarnated as an extra in a novel fated for death by the hands of the villain. What would you do if you were reborn at best? Escaping from her abusive family, she runs away and lives happily with her small dog, Momo. Unfortunately, her family eventually finds her and sells her off to be wed by the villain of the book. But when they meet, he claims to be Momo?
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○ Promo

After I escaped from the research facility, I was living a normal life—until I moved in right next to the female lead’s house. I realized I’d become an extra from the novel, as well as the female lead’s neighbor.
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○ : child abuse; human trafficking