Becoming Professor Moriarty's Probability - Chapter 4: The Scandal of the Bohemian Queen

This story is centered around the man named Yi Ji-Hyuk, who has spent 1000 years in a Medieval Western fantasy-like world before returning back to the modern-day Earth. When he returns, he finds that his home is facing monster threats, and that humans with superpowers have appeared to protect the innocent people of Earth.

Always looked down upon by others, Ji Feng gains technology far more advanced than the present, as he discovers its abilities, he begins to walk a path far from ordinary. With X-ray vision allowing his to find jade stones in rocks. With this futuristic technology, Ji Feng accomplishes something no-one can compare to. This is the beginning of a legend.

- Description from Novelupdates

Travel through Naruto and become the son of an ordinary civilian Chunin.

In this life-like world,

He obtained the golden finger to speed up the practice of ninjutsu,

Let ninjutsu itself produce a magical change from decay.

The knife cuts the jade, and the water bomb breaks Suzuo.

- Description from novelbuddy

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.