Toaru Majutsu no Index: Genesis Testament - Volume 1, Afterword

“While playing a Tsukkur erotic game that I loved, I somehow became possessed. To make things worse, I transformed into a perverted kid—one of the villains from the NTR series.”

Based on the popular Vocaloid song .

Rin, a young angel (presumed female, but angels don’t have clear genders) falls in love with a young human girl, Miku. However, their love is considered taboo, and so, Rin makes a deal with the devil to be reborn as the human boy, Len, in order to be with Miku. However, their happiness together is short-lived, and even that soon ends in tragedy.

Yang Qi was the son of the patriarch of a wealthy family from a small town.

Believing himself to be in love, he stole a pill for his lover, only to have the girl betray him, by taking the pill and leaving him behind.

Caught, his dantian was crippled and left to die under the lightning.

This lightning helped him to recover his lost martial arts and also helped him gain a new, divine-like cultivation technique.

After this second chance, he gains more power as he sought revenge and also to find about his missing mother….

This is a world where humans, demons and mysterious beasts coexist.

Humans cultivate mysterious qi. Demons cultivate corporeal bodies. Mysterious beasts cultivate soul perception.

A legend says that in the middle of an endless rainforest, there are extremely powerful existences; they are called demon kings.

Some demon kings have a tyrannical corporeal body, some are experts in illusions.
Some demon kings are proficient in magic, some can even move mountains.
Some demon kings are able to sense things thousands of miles away.

These demon kings rarely appear in the human world. Even if they emerge in the human world, they would reincarnate in human form; assimilating with mankind while seeking to breakthrough realms…

- Description from Novelupdates