Toaru Majutsu no Index: New Testament - Volume 13, Chapter 2: Run, or Die — Chase_With_the_Girl.

After she had transmigrated into the body of an abandoned wife of a little marquis in Ancient China, Su Nuan Nuan, a modern-day food lover was delighted!

On his coming-of-age day, Argolaith’s mistake bound him to a mystical magic unseen in the world. As his powers grow, they threaten to reshape the realm—but can he master them before they bring ruin?

I exist in the darkness, disappear under the bright light, and will eventually devour the sun and turn into the shadow of all things… Known by people as the indescribable terror of darkness; the king of shadows; the dark day; the existence of the shadow of the world , is still just a somewhat special high school student, facing a weird death game…

- Description from novelbuddy

After Reincarnating into Naruto World at the Warring State Era as an Uzumaki, Masahiko thought that he got a useless System. He lived for 48 years as a normal, below average Uzumaki Shinobi.

That changed when he finally knew how the system works the day of his 49th Birthday!

- Description from Novelupdates