Slime goes Back in Time, but with a Twist?

Prologue

It's been 420 years since The Great Tenma War and the world has been at peace since. Tempest has changed a lot since, merging together with its allied nations while sharing their resources. Tempest had successfully recreated a lot of otherworldly items with the help of skills and magic.

But enough with the introductions. Inside of a beautiful castle, inside a room full of paperwork, we see a girl(?) with long silvery-blue hair and bright yellow eyes sitting at his desk while talking with his manas. That girl(?) is Rimuru Tempest.

>> Hey Ciel-san? << Rimuru said to his manas in a bored tone.

<< Yes Master? >>

>> I– << But before he could finish, Ciel interrupted.

<< Before you could ask me to finish your paperwork for you, my answer is still NO >> Ciel said in an angry tone.

>> But I'm already done... <<

<< No means no- Wait What?! >>

Ciel said in surprise while using her analytic skills to check through all of the paperwork Rimuru did since she didn't trust him at all.

<< Wow, good job Master! >>

>> Fufufu, praise me more. << Rimuru said, with an impression resembling Ciel's.

<< ... >>

>> Anyways, now that I'm done with my work, I'm bored. What should I do? <<

<< Master could always travel to another world >>

>> No... I find it troublesome to have to reintroduce myself to a bunch of people I don't know. <<

<< Then what about visiting Milim or Guy? >>

>> No... <<

<< Then how about visiting Tempest? >>

>>I already did the last time I had a break... <<

<< Hmmm... >>

Ciel thought for a couple seconds while using {Thought Acceleration} and came up with this.

<< We could use Chloe's Ultimate Skill {Yog-Sothoth} to go back in time to the time when you were just reincarnated and restart building Tempest. >>

>> But why would I do that? <<

<< After analysing master's memories, Master for some reason really likes to restart a video game after you finished it. You have done this 273 times. >>

>> 273 TIMES?! Was I that bored in my past life?! <<

<< Yes. >>

>> Well, I still don't want to go through losing all my loved ones again. <<

<< You won't, master. You are already more powerful than anyone ever who posed a threat to us. Going back in time could also mean you could save people you previously couldn't. For example, 'your destined one' Shizue Izawa. >>

Although Rimuru still has that lingering regret for not being able to save Shizue, he never thought of saving her since she said herself that she doesn't want to be in this world anymore.

>> But didn't she say she hated this world? I would want to make her suffer any longer in this world. <<

<< But Master, wasn't the reason she wanted to leave this world is because how horrible it is? If you show her how wonderful this world could be, wouldn't that give her a will to live? >>

Rimuru thought for a moment and said:>> Alright you've convinced me. But who would manage Tempest when I'm gone? What if there's someone my subordinates can't handle? <<

<< You could make a parallel existence. >>

>> Oh right. How could I forget? <<

<< ... *sigh* >>

>> Did you just sigh, Ciel-san? <<

<< No, it's just your imagination. >>

>> ... Anyways can you create a clone of me? <<

<< Already done, Master. >>

Black smoke appeared around Rimuru and formed a clone right in front of him.

>> Alright. Let's go! <<

<<Hai. Using Ultimate Skill {Yog-Sothoth} to travel back when Master just reincarnated. Teleporting... >>

And so Rimuru and Ciel went back to the past. But unbeknownst to them, someone was secretly watching them.

(???): "Finally. " 

"After all these years. "

"You are finally going to mine. "

"Rimuru Tempest." 

____________________________________________________________

Yo. Author here.

This is my first ever fanfic so cut me some slack.

Hope you enjoyed this prologue.

Here's how the talking system works:

Benimaru: "Rimuru-sama!" = Dialogue

'Hmmm' = Thought

<< Master... >> = Ciel talking to Rimuru

>> Yes, Ciel-san? << = Rimuru talking to Ciel 

Alright, bye.