After the first century of closed cultivation, Raon left as he had been learning for longer, so he had already learned the things Junho taught earlier, which saved his time.
In that century alone, Altair's cultivation exceeded what Raon had achieved in his 200 years of age due to the massive resources and a personalized cultivation manual available to her.
One thing that Si-Eun noticed and told Raon was that Altair's talent in swords was lacking compared to Raon's, but she had above-average talent in every weapon, unlike Raon, who seemed to have talent solely for the sword.
Si-Eun taught Altair the way of the sword since she herself used swords as her main weapons, making Altair a sword user as well, but she could also use other weapons with high proficiency in them.
The difference between Altair and Raon would be that Raon transformed every weapon into a sword-like state and used them, but she used every weapon as it should be with great flexibility in switching them.
Her proficiency in other weapons was already nearing Raon's, despite the huge age gap of nearly five centuries, but Raon's proficiency in his sword was already quite close to his master's, making it a chasm away from Altair's.
Therefore, Raon decided to let Si-Eun continue teaching Altair using the methods she saw fit since he truly thought it would be better for her to be taught by someone other than him, as he knew that he was quite lacking in other departments barring the sword.
Content with his progress, Raon left the seclusion training as he needed to deal with other things, as Junho and Si-Eun also gave him many insights that he decided to implement as a ruler.
On one side, Raon was going out and attacking nearby territories to take over and merge them into his empire, increasing its size, Altair was forced to continue her cultivation in seclusion under her master.
Si-Eun and Junho were completely focused on teaching whatever suited her the best to increase her strength as well as leave their legacy behind.
She was better than Raon in every aspect, excluding the sword, meaning that her abilities in the side occupation also increased at a frightening pace compared to how slowly Raon progressed in them.
Her stable and steady cultivation naturally excited the duo of Masters teaching her, as they were already done with Raon due to his longer time spent with them, and Altair was better than Raon in every way.
The next two centuries passed similarly, with the two teaching Altair everything they knew and sparring with her from time to time, as well as Raon spending normal family time with her as any normal father would.
In the past three centuries, Raon had been able to envelop nearly half the territory in this region, making it on par with some Tier-2 empires in size alone.
Unfortunately, the overall average strength of his empire was on the weaker side when compared to theirs, so he couldn't just go and announce it to the world, but he wouldn't just watch them take it over.
Both his masters' presence became prominent when envoys from nearby empires arrived, as they were all here to take over the free meal that was the already widespread territory developed by someone else.
This was the reason they had completely ignored the growing presence of the Empire in the countryside earlier, but it came to bite them back in the ass as Raon brought his two Masters as backers.
Even Raon's current cultivation realm was already nearing the rulers of such empires, and Altair's realm was also not that far behind, to the point where they theorized that she would be able to surpass Raon if not for the massive age gap formed due to the time dilation formation.
At this point in time, both his Masters had finally given everything to Raon and Altair as their legacy disciples before telling them that they would have to return to the Upper Realm as their age limit for their current realm was nearing.
Si-Eun and Junho both could return to the Upper Realm, but they were waiting for as long as possible and allowed time to pass before the time they would be returning to be on the safer side.
Surprisingly, both of them had to do nothing other than break the seal placed on their cultivation and allow it to return to where it used to be, which would be at the limit of their world.
As soon as the two released their seals, massive amounts of energy gushed in their direction, forming a whirlpool of energy centered around the two.
The huge whirlpool formed a tornado, which created huge vortexes that were deficient in energy in the surrounding areas before their cultivation seemed to skyrocket, emanating huge shockwaves of energy outward.
Their cultivation kept rising before stopping at the limit of this world, and just then, both of them pushed through their breakthroughs to ascend to the upper realm.
They spent hundreds of Rank-6 Stones which were extremely scarce on this planet, yet the two didn't seem to care as they pushed for their breakthroughs with full fervor.
The phenomenon continued for several hours, eliciting a natural phenomenon-like event that invited countless uninvited guests to witness the bizarre spectacle.
The energy in that area was suddenly sucked dry as even the uninvited guests fell to the ground, unable to control their energy at all.
The space behind the two midair cracked after a very strong energy wave emanated from the two, startling everyone present as the energy of the surroundings became extremely chaotic.
"Goodbye and take care, younglings" said Si-Eun, audible only to Raon and Altair.
"Don't strive for only strength blindly, but diversify" said Junho, audible only to Raon and Altair in a similar manner, but he also threw a spatial ring hidden from others to Raon.
The two didn't say a word about their lives in the Upper Realm except for one thing before finally departing.
"The Upper Realm is far worse than what you can even imagine." Junho sent a telepathic message to Raon only as his final parting words.
The entire area went silent as they seemed to have evaporated in front of so many eyes, but it returned to a calm state as if the calm signaled the forthcoming of a storm.