Toaru Majutsu no Index: New Testament - Volume 17, Chapter 1: Or Cutting Off Leads to Diffusion - Gray_City.

16 years old-- most boys would be falling in love, as their hormones all rise to unprecedented levels. Most boys at Riley's age would have dreams; dreams that will slowly grow into passion. Riley, however, at age 16... killed the world's number 1 superhero.

Of the ancient gods only one remained in the world. This god lived alone for thousands of years and no longer had any desires. Legend had it that during the great war between the worlds he used his powers to turn the tide managing to seal the cataclysmic rift bringing order back into the three realms. Time flew by and hundreds of years passed in the blink of an eye.

One day, when a novelist woke up from a restless sleep,he realized that he had transformed into his 12-year-old self.

The most fucked-up separation in the world, is that there is a baby in your belly when you break up with someone.

Bo Yu draws on his cigarette, slowly puffing out the smoke, and looks at the little boy lying in bed with deep eyes.

Two years later, he finally comes back.

- Description from Novelupdates