Conclusion

Raina's PoV

A huge explosion happened as two opposing forces collide. The aftershock created was too ridiculous as we are barely able to avoid being thrown off. Even though thats the case we are still being pushed back.

Daddy has also placed a barrier to protect us from the aftershock of the explosion which started to crack. The world created by [Ars Paulina] has started to break down due to the mana being used to maintain it being used up during the explosion.

As the dust settles in we see the two of them a distance away from each other  with grins in their faces. Its been a while since Onee-chan showed an expression like that. The last time was when she and Ilya went all out in a spar.

The world created by [Ars Paulina] already broke down as we are now back at the training grounds.

"Haah, Haah. They went too far..." Ilya said while looking exhausted. She used too much mana in creating [Aegis].

Aegis was currently the strongest defensive weapon in Ilya's arsenal. It was the shield used by Athena that was said to be unbreakable. The shield can be unbreakable. That is if you have the mana to maintain its barrier or else it would break.

No matter how strong a weapon is it still depends on the user. Something that Ilya-neechan always says. Which I also agree with. Its the same for magic. It doesnt matter if its powerful, what matters is if you can use it effectively or if you can even use it an all.

The two who are barely standing then fell down at the same time. Both of them extremely exhausted.

The treasures in Onee-chan's sacred gear may be powerful but you need to be powerful enough to support them. That why most of the time she just uses Regulus as its not more taxing than others. She shoots them as its the way the gate should be used and also the most cost efficient way of using it. However activating the treasure's power like she had done is extremely draining. Thats why she wont use Ea unless cornered or so pissed that she really wanted that person to be erased from this world.

From what she told me she still cant use Ea to its full potential due to how powerful it is. The mana used would be really draining.

Its similar to using my ring's 3 special spells, one of which was [Ars Paulina] that I just used. It is capable of creating a world where the concept of death doesnt exist for a period of time. However each revival is extremely taxing and can cause the world to collapse faster.

They are powerful but can only be used as final trump cards.

I looked towards Daddy who is exhausted.

"Damn... good thing I didnt use the down fall dragon spear or Regina's attack would have injured me..." He muttured.

I then gave him some pills that are manufactured at Regulus Dominion.

"What are these?"

"Regeneration pill. It increases the time it takes for your mana to return to your body. With that Daddy's exhausted feeling from mana exhaustion will be gone in 5 mins." I explained briefly before going towards Onee-chan. Ilyanee-chan and Lilynee-chan have already taken their pills and is fine.

Me and Ilyanee-chan walked towards Onee-chan while Lilynee-chan went towards Onii-chan. We both gave them pills and waited for them to recover.

I thought back to the fight earlier and Im glad that Ilyanee-chan came with us or it could have been bad. [Aegis] was the one who took much of the blow earlier and could have caused more damage if Ilyanee-chan wasn't here.

...

Regina's PoV

Its been a while since I had a fight like this. We lost ourselves in the fight and forgot about the surroundings, Raina will probably scold me again for this.

Raina has given us some of the regeneration pills so that we could start recovering our mana again. Still, as expected using the treasure's true power really drains me. As I am now I still cant use Ea to its full potential.

I have to say Onii-chan really powerful. So much powerful than Issei though I do not know if that would be the case in the future.

...

I have already been scolded by Raina and now we are watching them scold onii-chan who just woke up. It seems using the [Juggernaut Drive] really drained him much more than I did.

Father told me that Onii-chan should be the strongest White Dragon Emperor to have ever existed probably even in the future due to his unique lineage as a descendant of Lucifer. Hearing that I felt bad for Issei who is his rival.

Onii-chan would probably get disappointed if he sees Issei as he is now. Onii-chan can already use juggernaut drive where as his rival still cannot even do a balance breaker. Well its to be expected as Issei has just awakened his sacred gear. We will see how he fairs in the future. If there is one thing that pervert has over Onii-chan its desire and determination. As long as he doesn't lose those things his sacred gear will grow stronger.

. . .

After Onii-chan had been scolded Ilya approached him.

"Nii-san... Fight me next." She said looking at him. It seems she got fired up watching the two of us fight and wanted to see how well she can do against Onii-chan.

Seeing this Onii-chan wanted to fight as well but was berated by Lily.

"Onii-chan you cant, You have just fought against Regina that hard you still need to rest."

Hearing that Onii-chan knew as well that he wouldn't be able to draw his powers as well as before due to his current state.

"Well, We can always do it later so you two don't need to worry." Said Father to the two who is disappointed in not having a battle.

"Everyone should rest up. Its almost time for lunch. So lets return upstairs." To which everyone nodded and headed back to the house.