The Aerial Fortress functioned primarily as a major power-up event for the Protagonist's Party. While it was certainly a pivotal moment for the plot, it served an even greater purpose as the location where players obtained the items essential for clearing the game.
In game terms, the story wouldn't progress unless this event was completed, but no such hard conditions existed in this world. There were only results—success or failure—and unlike a game, even a failure would see the situation continue to spiral forward.
Thrown into this scenario alone, Harold had a specific mission he needed to accomplish to ensure the story reached its proper conclusion: he had to seize the crystals that served as the power source for the fortress's levitation and flight.
There were six of these crystals in total, and they were originally the gems used to adorn the Secret Treasures that Harold had been forced to collect. Furthermore, the crystals themselves were ancient legacies said to have been carved out from the Planet's Core.
(If I'd known it would come to this, should I have just swiped the crystals beforehand? No, but still...)
Harold, of course, had known that the crystals from the Secret Treasures would become the power source for the Aerial Fortress.
As for why he had tamely handed the Secret Treasures over to Harrison, it was because there was a high probability that stealing a single crystal wouldn't have accomplished anything. If the Secret Treasures hadn't been decorated with the crystals, or if he had lied and said he failed to recover them, Justus would have grown suspicious and interrogated him. He could have played dumb, but once suspected, he surely would have been removed from the recovery mission.
Conversely, he had calculated that by being the one to recover them, he could gauge the progress of the plan and maintain some control over the timing.
Moreover, there were seven Secret Treasures in total, and one was already in Justus’s possession. Even if he stole one crystal, a spare existed, meaning the ascent of the Aerial Fortress couldn't be stopped.
There was also the fear that Justus might realize something was amiss if Harold acted out of character by stealing a crystal. What he wanted to avoid most was a deviation where Justus handled the Secret Treasures differently than in the Original Story, resulting in them never reaching the hands of Rainer and his companions.
The crystals likely would have still been used to power the fortress, but it wasn't hard to imagine that if all six Secret Treasures were kept under Justus’s direct lock and key, recovering them would have been an exercise in futility.
(If that happened, I might have had to face the Last Boss Battle against Justus with no Secret Treasures and only one crystal. If that were the case, we'd definitely be wiped out...)
In the fight against Justus, these Secret Treasures and crystals held the key.
Justus, having synchronized with the Planet's Core, became an existence that was essentially a mass of pure energy. Once that happened, normal attacks and magic were completely ineffective. In short, no matter how much one attacked, no damage could be dealt.
What was needed then were the crystals created from that same core, along with the Secret Treasures that served as their vessels. Only by equipping these would it finally become possible to hurt Justus.
The Aerial Fortress event was designed to grant the player the items mandatory for defeating the Last Boss.
And in an RPG, an item of such importance was naturally guarded by a boss battle. In the Original Story, it was Vincent who served as that boss.
At a time when he was mentally fragile due to a series of compounding tragedies, the game's version of Vincent was manipulated by Justus—the mastermind behind those very tragedies—and stood before Rainer and the others as a convenient puppet. Then, in a cinematic following the battle, he was struck down by his best friend, Cody, and sank into the sea along with the Aerial Fortress as it lost its power and crashed.
Incidentally, the reason Cody had been there was that he had transported the Protagonist's Party to the ascended fortress using an Airship he had "borrowed" through his old connections in the Knight Order. Well, "borrowed" was just how Cody described it; in reality, he had deceived his former comrades and stolen it.
He had gone that far because he had discovered Vincent was acting alongside Justus and was desperate to stop him. It was precisely because he was the kind of man who would go to such lengths that players often said if Cody had still been in the Knight Order when Vincent began to fall, he might have been able to keep him from the edge.
By some twist of fate, although the circumstances were quite different, that "what-if" scenario had been realized in this world. Even so, seeing Vincent fall into a brainwashed state—albeit temporarily—and having to fight those who opposed Justus made Harold feel the weight of the world's Correction Force. However, for Vincent at least, a better end than the one in the Original Story likely awaited.
Of course, that was assuming they could prevent Justus’s plan. To do that, he first needed to secure all the crystals.
The problem, however, was that he lacked both time and manpower.
(If it's like the Original Story, the six crystals should be installed in three separate locations. If I have to go around this massive fortress all by myself...)
No matter how he looked at it, it would take too long. He had the Dungeon Map from the game memorized to some extent, but as it was a distant memory, it wasn't perfect. Furthermore, the game map had likely been simplified for playability; the interior of the actual Aerial Fortress was almost certainly larger and more complex.
This was the only place in the game where a Warp System was implemented, but that only highlighted how massive the place was. Originally, the six party members would split into two groups, and the player would operate both parties from their respective perspectives.
Then, they would rendezvous in front of the final chamber and face the battle against Vincent with the full party.
While the game didn't have a strict time-attack element, allowing the Aerial Fortress to crash onto land would result in catastrophic casualties. That was why it had crashed into the ocean in the Original Story. A crash of such a massive object would cause great damage from the resulting tsunamis, but it would still be far better than it falling directly onto a populated area.
"Out of my way!"
He mowed down a Monster that appeared in his path with a single swing, running past without even checking to see if it was dead. Right now, he couldn't afford to waste a single step, or even a single second.
After running through the fortress for a while, occasionally dispatching monsters, something suddenly appeared before him. About ten meters ahead, an object abruptly burst out from a passage on the right. No—to be more accurate, it was blown out.
The object that had been slammed violently against the wall was the corpse of a monster.
As his wariness intensified, wondering who could have done such a thing, he laid eyes on the culprits. The doubt and caution inside Harold were instantly replaced by pure confusion.
"...Why the hell are you lot here?"
Emerging from the passage were Rainer, Vincent, and Erika.
If it were the full Protagonist's Party, he would be surprised but could understand it, but he had no idea why Vincent was with them. By what possible circumstances had this specific group boarded the Aerial Fortress?
"Lord Harold."
As Harold stood there dumbfounded, Erika suddenly stepped forward and closed the distance. She reached out, her right palm softly touching the area over Harold's chest.
(W-What...?)
Harold was bewildered, unable to read the meaning of her action.
Since she was looking down, he couldn't see her expression, but her hands and shoulders were trembling slightly. He couldn't tell if that trembling was from worry, anger, or some other factor entirely.
Come to think of it, from an outsider's perspective, Harold was currently a missing person. Given Erika's kind nature, she would have been concerned for his safety even if he were someone she despised.
On the other hand, if she was angry, he couldn't think of a reason why. Even if he was hated, that grudge dated back eight years, and he didn't remember doing anything recently to further earn her ire.
(Is she going to suddenly slap me here?)
He had already checked off that event during his childhood, but there was a non-zero possibility that some cosmic force would conspire to have her deliver another slap for some unexpected reason.
Well, he had no intention of quietly taking it, and as long as he was prepared, dodging it shouldn't be difficult. He remained on guard, but Erika's reaction was far milder than his cynical expectations.
"...Are you injured?"
"That's a foolish question. You can tell just by looking."
As usual, his mouth refused to offer a single honest word of gratitude for her concern. However, Erika, who was likely completely used to Harold's verbal abuse, didn't seem fazed. She slowly raised her head.
"Yes. Truly... I am so glad you are safe."
Erika spoke the words as if savoring them.
Her expression was a complex mixture of joy, relief, and a dozen other emotions. It looked unmistakably like something that had welled up from the very bottom of her heart.
Faced with such a smile at close range, Harold looked away, overcome by awkwardness.
After all, for the past eight years, he had consistently acted in ways intended solely to make her hate him. He was fully aware of the misery he had put her through. No matter how much it was a kindness stemming from her innate personality, having Erika worry over him like this felt incredibly uncomfortable.
Well, Erika had now officially become a member of the Protagonist's Party, so she likely wouldn't leave at this point. That meant there was no longer a need to intentionally make her hate him, but that didn't mean his mouth would stop its automatic hostility. Furthermore, Harold himself wasn't thick-skinned enough to think they could just let the past be bygones and be friends.
Even if Harold had his reasons for his past behavior, Erika didn't know them. From her perspective, if he were to suggest making amends now, she would be well within her rights to ask him who he thought he was.
In fact, a slap would be entirely justified.
"More importantly, answer my question. Why are you lot here? Are the others with you?"
"No. Only the three of us came here."
(Seriously, how did it turn out like this?)
Colette, Hugo, Lifa, and Francis, who should have been here, were absent. Instead, Vincent was accompanying them, and to make matters worse, the brainwashed Cody was somewhere in this very fortress.
From Harold's perspective, this setup was an omen of disaster. He felt like clutching his head and groaning.
"Harold, do you know where we are?"
Vincent, the man who shouldn't have been here, addressed him. Judging by his tone, they hadn't boarded knowing what this place was. The mystery only deepened.
"...A legacy of an Ancient Civilization. This is the interior of the Aerial Fortress."
"I see..."
It was likely a hard story to believe. Not just Vincent, but the other two also looked skeptical. However, Vincent swallowed his doubt and asked another question.
"I have a mountain of questions, but I will stick to what is necessary. Is it possible to escape?"
"Of course. But what do you intend to do about it?"
"I apologize for being blunt, but I would like to request that you take command for our escape."
Harold understood why Vincent would make such a request. Logically, it was the option with the highest probability of success. However, he also expected that Erika and Rainer might have some resistance to being under his command.
"Hmph. I don't mind taking command, but my orders are to be followed with absolute obedience. If you can handle that, I'll use you as my tools."
Erika didn't seem to have any outward objection, but Rainer was making a complicated face. Well, after they had opposed each other so clearly, it was only natural. Still, the priority was escaping the fortress. The fact that the situation on the ground was unknown was also a problem; if things were diverging significantly, a course correction would be necessary.
For that correction, the presence of Rainer and Erika was indispensable. Regardless of their personal grudges, nothing could be resolved until they were back on solid ground.
"I have no objection. What about you two?"
"I don't mind either."
"...Understood. Escaping is the top priority right now, right?"
"Then it's settled. We'll split into two groups. Rainer, you follow me."
Rainer, suddenly singled out, stepped back half a pace in surprise.
"W-Why me...?"
"There are two locations that must be dealt with first, but one is a significant distance from here. I have no intention of dragging a dullard along with me."
Erika and Vincent wouldn't be able to keep up with Harold's top speed. In exchange, it would be more efficient for them to head toward the closer power source. Erika, with her long-range firepower and support capabilities, and Vincent, as a high-durability vanguard tank, were a perfect match in battle.
It was by no means a decision based on thinking that being alone with Erika would be awkward.
"You're the only one among us with decent speed. If you fall behind, I'll leave you for dead."
"What—!...Fine! I'll definitely keep up with you!"
The usual vitality returned to Rainer's eyes and voice. Harold didn't think of him as being easy to manipulate.
As a character, Rainer was often criticized for being thoughtless. He was indeed impulsive and often missed Harold's irony, but Harold knew that he held deep feelings in his heart and that, as a boy his age, he struggled and lost his way just like anyone else.
However, he was a boy capable of facing those struggles without running away, shouldering his burdens and moving straight ahead. Through those experiences, the boy named Rainer Griffiths would grow and eventually become a knight worthy of being called a hero.
Kazuki Hirasawa—the soul within Harold—had always liked that protagonist. That feeling remained unchanged.
"Prove that those words aren't mere bravado, Rainer."