Spell Weaver - Chapter 81: Breakthrough

[You have entered the dungeon at Gwachun Station’s 1st Exit.] When former high school student Kang Woojin finds himself returned back to Earth after being forcibly summoned to a foreign planet for 20 years, he soon finds that Earth is not the same, normal place as he once remembered it to be.

Overnight, Tangning became a big slave owner in the southern United States with three large plantations and hundreds of black slaves who could be driven at will.

Tangning was very satisfied with the result of such a time-travel, but then he sadly discovered that he could only enjoy three years of such a good life, because three years later would be the “Civil War”, what should he do after this?

- Description from novelbuddy

An elder asked a young man if he wanted revenge for being humiliated by a strong man and disregarded by his master. The elder offers to pass his power to the young man, who is amazed to find centuries' worth of skill appear on his phone. The power is from the Heavenly Court, where users can borrow without interest for 30 days. The young man worries it might be a 'magic loan,' but the elder assures him that it is safe, as the daily interest is very low.Zhang Yu snorted coldly and closed the ad.

Yuki, a high school junior, dies heroically saving a stranger and is reincarnated in a fantasy world, where he discovers an extraordinary and unrivaled power.