Well, I gotta say this thought, 'leonardo18anime' has made a Highschool DxD/Dandandan Crossover which means that finally, Highschool DxD has aliens now so...

Yeah, I guess?

Anyway, on with the story.

Disclaimer: I do not own Highschool DxD and 'Straw Hats DXD2' by 'leonardo18anime'. They belong to their respective owners.

Enjoy.

Rias Gremory, her crimson hair cascading down her back like molten fire, had bid farewell to her peerage.

Yuuto, ever stoic and polite, nodded in acknowledgment while Akeno, with her ever-present gentle smile, offered a knowing glance and Koneko, quiet as always, gave a slight incline of her head, her cat-like eyes observing everything.

Dismissing them for the evening, Rias turned towards her mansion, the twilight casting long shadows around Kuoh Academy.

As she walked, her mind drifted to the usual concerns of a Devil Heiress. Peerage strength, territory management, and the ever-present need for stronger members occupied her thoughts.

Perhaps a skilled Magician? Or another unique Sacred Gear user? Lost in these strategic musings, a streak of light in the darkening sky caught her attention.

"A shooting star?" she murmured, a faint smile gracing her lips. It was a pretty sight, a brief flash of celestial beauty. But as she continued to watch, her brow furrowed. This 'shooting star' wasn't fading, it was growing larger, faster. The celestial beauty morphed into something alarming, a descending object of considerable size and speed. Her instincts screamed at her to take cover, but curiosity, and maybe a touch of devilish recklessness, kept her rooted to the spot.

The object plummeted to earth with a thunderous crash, the ground beneath Rias's feet trembling violently. Dust and debris billowed into the air, obscuring the point of impact. When the dust began to settle, an odd metallic scent tinged the air, unlike anything she had encountered in the supernatural world.

Intrigued and now undeniably concerned, Rias unfurled her crimson Devil Wings. They snapped open with a soft whoosh, catching the evening breeze. Propelled by her wings, she ascended into the air, heading towards the source of the crash. As she approached, she could make out the shape of the object – it was undeniably a vessel of some kind, nestled awkwardly in a small clearing in the woods, its form radiating an unnatural, almost organic green glow.

It is a spaceship, there was no other word for it.

The design was unlike anything she had ever seen, sleek curves and bulbous protrusions giving it a distinctly bio-organic feel and parts of its surface shimmered with an oily sheen, while other areas were scarred and blackened from atmospheric reentry.

Rias circled the wreck cautiously, her mind reeling.

Spaceships?

Aliens?

It sounded like something out of a human fantasy novel, certainly not something she expected to encounter in her life as a Devil.

Shaking off her initial disbelief, Rias focused on the immediate situation such as how someone, or something, had just crash-landed on her territory.

Protocol demanded investigation, and her own curiosity demanded answers. She landed near what seemed to be an entry point, though it was mangled and distorted from the crash. Examining the alien craft, she noted the strange textures and materials, nothing she recognized from the human or supernatural realms.

With a determined sigh, Rias raised her hand as the crimson magic circles materialized around her palm, crackling with destructive energy.

"Power of Destruction," she whispered, unleashing a concentrated blast of red energy towards the damaged entrance. The organic-looking material groaned and splintered under the assault, finally bursting open with a shower of sparks and alien fragments.

Holding her hand out defensively, ready to unleash another blast at the slightest provocation, Rias cautiously stepped inside the wrecked vessel. The air inside was thick with the same metallic scent she had noticed outside, mixed with a faint, unfamiliar musk. The interior was dimly lit by flickering panels of light, casting long, eerie shadows that danced along the curved walls.

As she moved deeper into the ship, navigating through twisted metal and sparking wires, the sheer absurdity of the situation washed over her again.

Aliens.

Real, living aliens.

Here, on Earth, in her territory.

A Devil, a creature of myth and legend, encountering something thought to be purely fictional in the human world.

The irony was almost comical.

She reached what appeared to be the cockpit, or pilot's area as it displayed strange instruments and glowing screens surrounded a large, contoured seat.

And in that seat, slumped forward, was…him.

Rias's breath hitched as her initial shock and disbelief morphed into stunned awe.

Strapped into the pilot seat was a being unlike anything she had ever imagined, a being undeniably alien. He was clad in a green spacesuit that hugged a powerfully built, yet lean, physique. The suit featured a high, carapace-like hood that obscured most of his face, but Rias could see a portion of his head – smooth, almost featureless, entirely blank in expression.

He was imposing for sure, even when he unconscious and he looked like something ripped straight from the pages of those human sci-fi mangas Akeno occasionally indulged in, stories she'd always dismissed as fanciful human creations, attempts to explain the unknown through fabricated worlds of advanced technology and impossible creatures.

And yet, here she is, a Devil, face-to-face with something that defied her own understanding of reality.

Doubt gnawed at her.

Could this be some kind of advanced illusion?

A trick of the Fallen Angels?

But the smell, the feel of the alien metal, the sheer strangeness of it all… it felt undeniably real.

Cautiously, Rias approached the alien pilot. She reached out a tentative hand, her fingertip brushing against the hardened carapace of his spacesuit's hood. The moment her finger made contact, the blankness of his face vanished. Suddenly, two slits in the hood snapped open, revealing eyes that blazed with an intense, emerald green light. He jerked in the seat, a muffled groan escaping from within the helmet.

Rias recoiled in fright, stumbling back as the alien thrashed weakly in the straps, his glowing green eyes wide and unfocused. Then, just as suddenly as they appeared, the emerald lights flickered and died, plunging the alien back into unconsciousness. He slumped forward once more, his form still and silent.

Rias stared at him, her heart pounding in her chest. He was alive. A living, breathing alien. The implications were staggering. For the supernatural world, for the human world, for everything.

Ignoring the fear and the overwhelming sense of the unknown, a new feeling began to bloom within Rias – a sense of responsibility, of protectiveness. He was injured, vulnerable, and stranded on her territory. As a Devil, as a Gremory, it was her duty to act.

"I can't just leave him here," she murmured, her voice barely above a whisper. She knew what she had to do. She had to get him back to the Gremory Mansion, to safety, to… somewhere she could figure out what to do next.

But as she looked at the imposing form of the unconscious alien, still strapped into the pilot seat of his wrecked spaceship, the question echoed in her mind.

"Now, how am I going to get him out of here?" The sheer logistical nightmare of transporting an alien, a spaceship wreck, and keeping it all secret from the human world and potentially even other factions, began to dawn on her, and Rias Gremory, the Crimson Princess, felt a tremor of something she hadn't felt in a long time – genuine, profound uncertainty.

Well, that's all done about it.

If you have anymore ideas, let me know in the comments below.

As always...

Ciao...