The Fallen Vampire - Chapter 7: Time in The Dark

After getting betrayed and killed by the only person she’d loved, Miss Shang wakes up in the body of the cowardly crown prince Shang Wuxin, who, due to her own circumstances, was actually a girl cross-dressing as a boy. After inheriting the crown prince’s memories, Shang Wuxin has three things on her agenda:

1. Clean up the house

2. Gather loyal followers and soldiers

3. Get the throne

- Description from Novelupdates

Once she crossed through, she actually became the disfavored third WangFei?

With the memory of a Level 200, Tier 3 Mage. Lu Yang returned back to his life ten years ago. Destiny made a joke with him. He was betrayed and everything he worked for was taken away. He had to get it back.

The game’s money making methods, dungeon strategy, legendary quest, equipment source, secret blueprints, combat skills. He knows all. See how a reborn player with his brothers swept the country, burned the world and created the legend of The Fire God!

- Description from Novelupdates

The world was once at war with 10 alternate worlds. This was known as the Concept War and our world won 60 years ago. All of this was concealed so no normal people are aware of this fact in the current time.

After the death of his grandfather, the high-school student Sayama Mikoto is suddenly summoned by the giant corporation IAI. He learns this world is headed for destruction due to the acceleration of the Minus Concepts. To prevent this, negotiations must be undertaken with the survivors of the other parallel worlds so their 10 concepts can be released.

And so Sayama is caught up in the final battle to clean up after the Concept War which left behind so much enmity.