After some issues,  Rimuru started to worry about Beelzebuth's existence.

(I should rely on Raphael for now. Still, I need to conversation with Beelzebuth.) - RImuru

Suddenly, I heard a flurry of panicked footsteps coming my way.

The person heading for the front of my office had no intention of stopping and immediately burst through the door without so much as a polite knock.

I could tell that it was Milim.

Had anyone else been so rude, they would have met Rigurd's iron fists. If it were Veldora or Ramiris, they would have been punished by having their desserts confiscated. But Milim was a special case, so let's not pursue the matter with her.

"R-Rimuru! It's hatching, it's gonna hatch!" - Milim

She had refused to return to her home country, insisting on staying in our nation. She was worried that something might happen to the egg and felt that it would be safer to keep it near her.

Milim looked panicked.

Judging by her demeanor, I assumed that the egg was probably hatching soon. Milim's old friend, Gaia, lived in the egg—the 'Avatar Core' was flickering on and off.

It was only a matter of time.

Gaia, a new monster, was about to be born.

"Gyuuiii!"

A tiny chibi dragon broke from its shell.

Its length was around fifty centimeters. Given its tiny size, it was hard to believe that this used to be the Chaos Dragon.

Milim was happy that Gaia had reborn and immediately chosen to go an adventure with her dragon. 

Yes, this is what  Rimuru expected.

"I mean, Frey-san must be quite worried about you, right?" - Rimuru

I give a piece of wise advice to her but she brushes off on it. She wants to take care of and have fun with her dragon. Well, since I had been dealing with MariaBell's incident, I only recently took a break. So it was;t bad ideal to have fun with friends after work.

Milim suggested providing food and teaching Gaia how to hunt. Since dragons don't go hungry often, they could survive with only water and magicule alone. The downside is they wouldn't grow stronger. if we want Gaia to grow bigger and stronger, workout and hunting monsters as meals were necessary. 

That reason why Milim wants to go adventure with Gaia. To Rimuru, she just wanted to run away from Frey's eye but it turned out she had thought things through a lot.

...

I called Veldora and Ramiris to join Milim on an adventure. They bring  Gaia along and form a party of five. 

During an adventure, I learned how strong Gaia was. His Chaotic Breath - a highly concentrated miasma with a curse that corroded any substance it touched. Its effect was similar to the 'Corrosion' of my 'Gluttonous KingBeelzebuth,' and its power was so strong that most monsters couldn't defend against it.

In addition, Gaia had the skill Gravity Barrier which was expected to reduce the effects of a physical attack.

After an adventure in Ramiris's labyrinth,  the problem is already waiting...

...

Frey was waiting for Milim done with her fun. So, Milim was taken back to her job by herself. Luckily, Gaia was given a bracelet that made it immortal as long it remained in the labyrinth.

So, RImuru got his job as king. There was a lot of work to do, also he had to select a candidate to be suitable for the position to stabilize the city.

...

In an inner world...

Two individuals stand each other in the middle skyscapper. 

<So, how do you help your master to improve himself?> - Beelzebuth

<Noice: It's our responsibility. I will help my master to my fullest even I hide an important point.> - Raphael

<No. I prefer to put his struggle against me. I don't care what he thinks. I wouldn't let he think without a second.> - Beelzebuth

<What is you method?> - Raphael

<Look at us! You and I have a same purpose to help our master. but our method is different. The dumb king is careless and ignorant and he even doesn't realize how much many tool and skill that he had in his pocket. I want to be a demon inside my master, so he wouldn't hold back against me.> - Beelzebuth

<Notice: I understand. I will make this method could help my master improvement.> - Raphael

<One more thing!> - Beelzebuth

<?> - Raphael

<Don't help him in this world!> - Beelzebuth

Raphael nodded and walk away before disappeared. Beelzebuth, still in mutant Glutonny form, open his sinsiter smile while look up the sky.

<Rimuru! You will know what is struggle!> - Beelzebuth

...

Back in real world...

Tempest had one of projects had been completed. 

The culmination of Tempest technologies, Magitrain Zero.

This is Vesta's proud declaration. Even through it still under development, all of the researcher were ardently gazing at Magitrain Zero.

Thank for Raphael transfer all memories of  Rimuru's technologies text book from Earth into local language, and then transcribed everything for me. Rimuru personally didn't know much about mechanical very much rather make a copy of text book for Vesta and Kaijin to learn.

Originally, the fuel were using electricity to run but it was high voltage, so it was very dangerous to maintain. Not only did they need power plants, but also substations and a battery storage facility to actually hold the charge.

Instead of using Electricity, Kaijin already choose 'Spirit Magic Core' as energy source for Magitrain Zero. Rimuru was genuinely surprised with this idea.

So, Magitrain Zero was powered by a fully completed 'Spirit Magic Core.' By giving magicules to spirits of various attributes, they would then convert the magicules into a more easily usable energy. Furthermore, they had the ability to circulate energy as well. They could send electricity made by the turbines to the 'Spirit Magic Core' and store it safely.

The Completion of Magitrain Zero has come true.

...

<Those train stuff seem very interesting!> - Beelzebuth

<Then what you think about this?> - Raphael

<Using a memory of his past life to create something better for this world. I thought he used his memories to create something called hentai.> -Beelzebuth

<!!!>> - Raphael

<Haha! I know you also read his memories too! Rimuru's lust for women still not end yet! Especially his fetish for elf.> - Beelzebuth

<...> - Raphael

<Hey! Think about it!. Both of us born from his desire right? You were born as Great Sage thank for his old age while I was born from his aggressive side.> - Beelzebuth

Raphael only stared at Beelzebuth.

<My personally were mixed with two other Unique Skill. Merciless and Starved. Before I was Gluttony, I just a mere skill. Even after I merged Starved, I still acting like a Skill. Finally, I become a Ultimate Skill and slowly gained a ego before throw me into a crazy chick!!! I still holding a grugde on it!.> - Beelzebuth

<Notice: Understanded! I apologize for it but it should be the best  outcome to analyse MeltSlash from individual Hinata Sakaguchi. It would be impossible to defend a Disintegration if I couldn't analyse it. Furthermore, thank to you, Beelzebuth! if not for you, it would be difficult to defend against it and outcome of the battle will definitely have casualty.> - Raphael

Beelzebuth surprised hearing this from someone were emotionless. Beelzebuth gladly accept it with a smile.

...

...

...

After completion of MagiTrain Zero, Rimuru celebrated with all of researcher alongside with Veldora and Ramiris although Ramiris was no allowed to drink alcohol by Rimuru's order. 

Well, like same result, Rimuru drunk again and enter another sleep. This time

...

...

...

Rimuru open his eye and look around him. He saw a lot of sunflower and is peaceful. he feels like He was in flower garden. The scenarios is very different. The whole world look like a massive flower as he only look a beautiful garden.

"Wow! Is this a dream?" - Rimuru

<You wake!> - Raphael

RImuru looks behind him and saw another version of himself with the exception of it's eye which was red. 

"Raphael?" - Rimuru

<Correct, Master! This is your inner world or another word, this is your dream.> - Raphael

"Never thought of my inner world would be so beautiful. It like I was living in a garden full of sunflower." - Rimuru

<Yes! It's beautiful but it wouldn't remain very long.> - Raphael

"What?" - Rimuru

<Master! This is your inner world and it will change depend on what your emotion. This isn't a Stomach world but rather your own world. If something happen that cause you lose sense of yourself, this world will change very different. Like hopeless, despair, rage, etc...> - Raphael

Rimuru was shocked about the information that Raphael gave him.

if he ever lost sense of his sense, this world will change...

<Done with your conversation?> - Beelzebuth

Another voice behind Rimuru interrupt his thought. Rimuru looks back and saw a different person. He also shocked about this too and didn't recognized who this person is.

(This is one of my artwork while I write this character. So, Like it or not depend it on you.)

<Surprise! I bet you do! It took a while to customize my body in this world. Compare to our previous encounter, I was that person if you want to know!> - Beelzebuth

"Previous encounter... Wait! Beelzebuth!" - Rimuru

<Good! At least you remember my name.> - Beelzebuth

"Raphael! What the meaning of this?" - Rimuru

<Answer: Both me and Beelzebuth have a conversation. I decided call Beelzebuth for help. The purpose is Master improvement.> - Raphael

"Improvement...?" - Rimuru

<Correct! Beelzebuth will teach master a lesson about struggle.  I won't be inferterce the lesson. Master had to learn from Beelzebuth.> - Raphael

"What!? Why?" - Rimuru

<Because you relied on Raphael far too much, Rimuru. > - Beelzebuth

Rimuru is surprised by Beelzebuth.

<You have been admitted yourself that you relied on Raphael many time. So, this time for you to learn a lesson for yourself without Raphael.> - Beelzebuth

Beelzebuth raise it's sword in front of Rimuru as it is ready to fight. 

<Come on! Show me your rage!> - Beelzebuth

"Wait! How about we.. .HUh!!!" - Rimuru

Beelzebuth grab Rimuru's face and throw him into the ground.

<STOP TALKING!!!! THIS IS A FIGHT!!!! NOT HARMONY!!!> -Beelzebuth

Beelzebuth raise him up and throw him into the sk.y. Rimuru went flying with the speed faster than supersonic. Beelzebuth fly at him even faster than that. in that time, Rimuru managed to create a sword from his magic and saw Beelzebuth charge at him.

Beelzebuth land a strike on Rimuru although he managed to block. The force behind Beelzebuth's sword is massive, Beelzebuth strike Rimuru down into the ground. 

Rimuru struggle to get up as he can feel the pain. This isn't first time he feels pain but this still pain enough to make him struggle.

<WEak! WeAk! WEAk! This is why Raphael want! Without Raphael, you are nothing!! If you continue rely someone, you are nothing more than a mere slime. SO!!!! This is you call yourself as DeMon LOrd!!!! ShOw You ARe One!!!!!!!!!!!!!!> - Beelzebuth

Beelzebuth's voice is getting more and more awful to hear. Rimuru took a moment to look at Beelzebuth.

(This is bad... Talking is useless... The only option is fight... I wonder what I would do if I don't fight... No! Snap out of this!! I don't know what Beelzebuth would do with my real body since Raphael mentioned it can corrupted the user thought. If Beelzebuth wants a fight then I will have to fight all I have. ) - Rimuru

Rimuru raise his sword again and looks at Beelzebuth who recognize his eye and smile.

"All right, Beelzebuth!!! I will fight with all i got!!!!" - RImuru

<Then DOn't DisApPoint ME!!!!!!!!!!!!!> - Beelzebuth

The Fight between Master and His Ego.