Toaru Majutsu no Index: New Testament - Volume 3, Chapter 5: For What Purpose Should That Strength Be Used? The_Old_Glory.

Mission: Transmigrate world by world into a scoundrel’s body; clean up the original’s life.

Wei Mingyan is a liar, through and through. But he doesn’t see himself as such. His motto? “If one deceives others for a lifetime, then all lies would become the truth.”

- Description from Novelupdates

I gave them my everything.My time… my strength… my heart.I trained while they slept.I smiled when they laughed.I stayed… even when it hurt.And what did I get?Nothing.They looked at me like I was pathetic.Like, I didn’t belong.Like I was… less.But I... the naive person I am, continued trusting them.They told me to act like trash, fine—I became trash.They told me to act like a scumbag, fine—I played the role.However...One mistake, one single moment...That’s all it took.And they threw me away.But now…Someone else woke up in my body.A stranger, a man who doesn’t know the pain I suffered, but wears my face.Let’s see what he does with it.Because me?I’m done with this life, so to the soul who took over my body...This is your mess now…'Gray'.

Yggdrasil, the World Tree of Norse Mythology, suddenly appeared on Earth. And with it came demonic creatures that ravaged entire cities.Although not all hope is lost, due to the System that a few special humans had gained.In this new world where only the strong survived, Min JaeHyun scrapes by regretting the wrong choices he’d made in the past… when one day, he gains the only Mythic item in the world.How will this item help him? And can he change his wretched fate?

“No matter what I would do, my actions would inevitably change the story. I knew this already.... But what do you mean that I changed the plot even before reincarnating in the novel!? ”

...

Should I follow the plot of the novel? Or should I do as I wish? Maybe I should follow the plot while making changes favorable to me?

These would be the first questions of those who reincarnate inside a novel. However, due to a certain event, Sol didn't have that luxury. He had already influenced the plot.

The change he created wasn’t small either. If nothing was done, the novel would head for a 100% certain bad end: Destruction of the multiverse.

Luckily for Sol, the plot of the novel had yet to begin. It would take a few months before everything starts in earnest and all the dimensions combine, bringing along the dying worlds and their catastrophes for the Great Merge.

“Yes! I will enjoy my life to the fullest!”

Calamities? Future Catastrophes? Inevitable Destruction?

Sol doesn't care for those things. He has a single aim, to live a life that would make even the Gods jealous!

Be it the hero who brings hope, the villain who crushes the protagonist, or the enigma who controls everything while staying in the background. Sol will switch to any role that benefits him.

But will everything go as he has planned? The longer Sol lives in this new world, the greater mysteries he comes to face. To start with, his new identity itself is….