The sun dipped low on the horizon as Kia led Senku and Taiju toward a towering ruin nestled in the shadow of the mountains. The structure loomed against the sky, its jagged edges softened by time but still commanding an air of forgotten grandeur. Vines curled along the ancient stone walls, but as Kia approached, there was a faint hum in the air, a whisper of energy lying dormant beneath the surface.

Placing her hand against a wall engraved with intricate runes, Kia murmured a phrase in her Atlantean tongue. In response, the runes glowed to life, pulsing with an eerie blue light that spread outward in ripples. The entire castle seemed to awaken, its walls humming with power and its halls bathed in the soft glow of light that resembled electricity but felt… alive.

Senku's eyes widened in awe, his breath catching in his throat. "This isn't just electricity," he murmured, running his fingers along one of the glowing walls. "This energy is biological. The whole structure… it's alive!"

Kia turned to him with a playful grin, clearly enjoying his amazement. "Only a citizen of Atlantis can light the way," she said with a note of pride. Holding up a glowing blue stone, she added, "We mine these stones from the depths of the sea. They resonate with the living stone of Atlantis, activating its dormant energy."

Senku's analytical mind went into overdrive. He leaned closer to the glowing rock, squinting as he studied its faint fluorescence. "Is it sodalite?" he asked, his voice tinged with excitement. "The fluorescence under UV light is uncanny—"

"It's a variation," Kia interrupted, smirking at his enthusiasm. "It evolved over millennia through contact with Atlantean living stone. But it's not like your land-based minerals. The energy is symbiotic—it requires a connection to its host." She held the stone closer to him, her expression almost challenging. "I don't think a surface-dweller could ever truly understand it."

Senku's gaze snapped to hers, his curiosity sparking even brighter. "Try me."

Kia rolled her eyes but couldn't suppress a faint smile. "If you're so determined… it's a pity we can't use the Ketaks to make the journey easier."

"Ketaks?" Senku's interest piqued instantly. "Show me. Bet I can get them going."

Kia's smile turned into a skeptical smirk. "They haven't worked in centuries. If you must waste your time…"

She led them deeper into the castle, through halls lined with glowing runes and walls that thrummed softly beneath their feet. They stopped before a massive chamber where several large fish-like machines lay dormant. Their stone bodies were smooth and intricate, with delicate fins carved into their sides. Their eyes were dark blue orbs embedded with the same glowing stones Kia had shown earlier.

"They're Ketaks," Kia explained. "Living transport. We used them to travel great distances through the water, but they've been inactive for over three thousand years. Their symbiotic systems require a compatible host."

Senku stepped closer, his hands tracing the lines of the nearest Ketak. He crouched, examining the structure, the intricate carvings, and the faintly glowing stones embedded in its surface. His face lit up with pure excitement, his mind racing as he pieced together its mechanisms.

"This isn't just engineering," he said, his voice barely above a whisper. "This is a fusion of biology and technology. A living machine… this is incredible!"

Kia crossed her arms, watching him skeptically. "Don't get too excited. It's useless without—"

Before she could finish, the Ketak stirred. Its stone fins twitched, and its eyes flared to life with a brilliant blue glow. The soft hum of energy filled the chamber as the Ketak began to move, its body rising from the ground as though awakening from a long slumber.

Kia gasped, taking a step back. "What—?! Those haven't been active in millennia!"

Senku turned to her, just as shocked. "I—I don't know! It just… it asked to be friends or something!"

"Symbiotic compatibility…" Kia whispered, her voice trembling with disbelief. "But that's only possible for the royal family…"

Senku's shock faded into a wide, triumphant grin. He leapt onto the Ketak's back, his excitement palpable. "Well, guess what, Princess? I'm ten billion percent compatible. You gonna keep asking questions, or are we saving Atlantis?"

He extended a hand toward her, his eyes sparkling with a mix of confidence and challenge.

Kia hesitated, staring at him as if seeing him for the first time. His enthusiasm was infectious, and the sincerity in his expression made her heart skip a beat. Slowly, she reached out and took his hand, allowing him to pull her onto the Ketak.

As she settled behind him, Senku smirked over his shoulder. "Hey, that's the first time you've smiled at me. You look better when you smile, Princess."

Kia blushed furiously, looking away. "Shut up and fly, surface-dweller!"

Senku chuckled, nudging the Ketak forward. The living machine responded immediately, its fins pulsing with energy as it lifted into the air, gliding effortlessly through the glowing chamber. Kia held onto Senku tightly, her initial embarrassment fading into wonder as they soared through the castle.

For a moment, neither of them spoke. The hum of the Ketak and the glow of the castle enveloped them in a surreal serenity.

Finally, Kia broke the silence. "You're different from what I expected, Senku."

"Yeah?" he said, glancing back at her with a grin. "How so?"

"You… don't just see our technology as a tool. You respect it. You're excited by it. You… make me think that maybe we can save Atlantis. Together."

Senku's grin softened into something more genuine. "That's because I'm ten billion percent sure we can. Your science and mine? They're better when they work together."

Kia's blush deepened, but she didn't look away this time. "You're… very strange, scientist."

"And you're very stubborn, Princess."

She smiled faintly, leaning into him as the Ketak carried them higher, toward the distant ruins of the Castle of Skye. For the first time, Kia felt a glimmer of hope—not just for Atlantis, but for herself. And as they flew together, she couldn't help but wonder if this strange, brilliant scientist might be more important to her future than she had ever imagined.