The Seyoung estate's library was everything Eren had heard about and more. Ancient scrolls lined walls of polished jade, their qi-infused paper giving off a soft luminescence as he followed Soo between the towering shelves. Crystal formations grew naturally between ancient texts, their facets reflecting and refracting energies into rainbow patterns.

Watching her move with such natural grace, Eren found himself increasingly distracted. The way her dark hair caught the crystal light, how her hands gestured as she searched for a particular scroll, the subtle shifts of qi around her like a constellation given form...

Then it hit him – quick as lightning, a flash of... something. Her face, but different. Tears. A scream that felt both foreign and achingly familiar. "EREN!"

He blinked hard, his shadow mana wavering slightly. What was that?

"Are you alright?" Soo asked, noticing his momentary distraction. "Your energy pattern just... flickered."

"I'm fine," Eren said quickly, though something in his chest felt heavy, like an echo of pain he couldn't quite remember. "Just... thought I remembered something. It's nothing."

Soo's qi phoenix, still perched contentedly in his hair, trilled softly. She smiled at the sight, then gestured to where his shadow mana was creating gentle patterns in the air. "I've never seen anything quite like it. In the murim world, we work primarily with qi – internal energy that can be cultivated through training. But your shadow mana... it's different."

"It's extremely rare," Eren explained, watching the darkness swirl between his fingers. "Only the Valestrixian bloodline has ever manifested it. Even we don't fully understand its nature. Some scholars believe it draws power from the void between realms."

"Like light mana?" Soo asked with scholarly interest. "I've read about how it was once incredibly rare until the great mutation."

Eren nodded. "Light mana users were almost extinct at one point. Now it's more common, though still hereditary. But shadow mana..." He created a small shadow butterfly, watching it flutter between them. "Many have tried to replicate it. That's how dark mana came to be – a failed attempt at copying our bloodline's power. But dark mana is unstable, dangerous. It consumes its users."

"We have similar cautionary tales about demonic qi," Soo said, her expression turning serious. "The Heavenly Demonic Cult uses forbidden arts that corrupt body and soul. That's why most martial artists stick to traditional qi forms – blaze qi for offense, ice qi for defense." She demonstrated, her energy shifting between scorching heat and crystalline cold.

This tale has been unlawfully lifted from Royal Road; report any instances of this story if found elsewhere.

"Yet qi seems more... accessible," Eren observed. "In the magical kingdoms, you're either born with the ability to use certain mana types or you're not. But here..."

"Anyone can learn to cultivate qi through proper training," Soo agreed. "Even sword qi, which was once considered special, is now commonly practiced. It's all about dedication and technique." She paused, watching where his shadow mana was unconsciously reaching toward her qi patterns. "Though I've never seen qi interact with mana quite like this."

Above them, Min's excited voice drifted down: "The resonance patterns between hereditary mana and cultivated qi are completely unprecedented! Jin, if we could just set up a few monitoring crystals-"

"Min, for the last time..."

"But Jin! This could revolutionize our understanding of energy interactions! The theoretical implications alone-"

"If you don't stop right now, I'm telling Father about the time you tried to combine blaze and ice qi in the meditation hall."

Soo laughed at their bickering, the sound making the qi phoenix trill happily. "Min's enthusiasm aside, he's not wrong about the unusual interaction. Normally, qi and mana resist each other. But your shadows..."

Eren watched as his shadow mana continued its gentle dance with her qi, creating patterns he'd never seen before. "Maybe it's because shadow mana exists in the spaces between – not just between realms, but between different forms of energy itself." The shadow butterfly landed on a nearby crystal, its wings rippling with hints of her qi where their powers had merged.

"Or maybe," Soo said softly, reaching for an ancient tome bound in midnight blue leather, "some powers find ways to work together, even when conventional wisdom says they shouldn't."

Their eyes met for a moment, and something deeper than magical theory passed between them. Then Eren looked away, that strange memory-flash still haunting the edges of his mind. His shadow mana pulsed gently, almost shyly, continuing its dance with her qi.

"The old texts," Soo continued, opening the book, "say very little about shadow mana. Your bloodline has kept its secrets well. But there are theories about energy resonance that might explain what we're seeing."

"Speaking of unprecedented resonance patterns-" Min's voice started again.

"Min," Jin's tone held infinite patience worn thin, "if you don't come down from there right now..."

Eren found himself smiling despite the lingering unease from his earlier vision. "Does he always get this excited about magical theory?"

"Always," Soo confirmed with a warm laugh. "Though in this case..." She gestured to where their energies continued their elegant spiral, defying centuries of established magical understanding, "perhaps his excitement is justified."

The qi phoenix chose that moment to hop from crystal to crystal, trailing sparkles of energy that his shadow mana playfully chased, while Eren tried not to think about why her smile seemed to echo through centuries he couldn't remember living.

After all, they had magical theory to discuss. Even if something about the way their powers danced together felt as ancient as the stars themselves.