The departure from the mountain was a familiar, yet fundamentally different, ritual. Ganyu, her heart now a calm, steady sea of love and trust, gave Ren a final, tight, and very long, hug.
"Promise me," she whispered, her voice a soft, earnest plea against his hair. "No more absorbing new elements. Please. My heart cannot take it."
"I promise, big sister," he replied, his voice full of a genuine, sincere, and now very well-informed, conviction. He had no desire to ever repeat that terrifying, world-altering experience again... unless absolutely necessary.
Shenhe, who had been a silent, watchful presence throughout their reunion, also came to say her own, unique, farewell. She was, as always, a being of few words. She simply stepped forward, her glacial-blue eyes holding a new, almost imperceptible, flicker of a soft, protective light. She reached out, and with a touch that was as gentle and as rare as a snowflake in a summer desert, she gave his head a single, soft, and surprisingly affectionate, pat. It was, for her, the equivalent of a long, emotional, and very tearful, goodbye. She then gave a curt, respectful nod to Xianyun and, with a silent, graceful movement, she was gone, a silver-haired shadow melting back into the vast, lonely mountains she called her home.
With their goodbyes said, Ren and Xianyun were left alone on the quiet, windswept peak, the air buzzing with a new, exciting, and slightly dangerous, scientific energy.
The first few days were a blur of demonstrations and analysis. Ren, now free to fully explore his newfound abilities under the watchful, and incredibly curious, eye of his Master, showed her everything. He showed her the crackling, violet lightning that now danced at his fingertips, a power that was as natural and as intuitive to him as his own, innate Cryo.
The true marvel, however, was the flight. He no longer needed his hoverboard. He would simply gather the Electro energy within him, and a soft, crackling, violet aura would wreathe his body, lifting him effortlessly from the ground. He would soar through the air of the mountaintop, a living, joyful bolt of lightning, his movements a perfect, graceful ballet of pure, elemental freedom.
Xianyun watched, her scholar's mind in a state of pure, ecstatic bliss. She took meticulous notes, she made complex calculations, she used her adeptal senses to analyze the flow of his energy, the stability of his flight. She was a scientist who had just been given the most fascinating, and most miraculous, research subject in the entire world.
After several days of this exhilarating, initial testing phase, Ren, his mind now turning back to their other, more mechanical, ambitions, asked the question that had been lingering in his thoughts.
"Master," he began, as he glided to a soft, gentle landing beside her at the stone table. "What about… the hovercar?"
A brilliant, excited, and deeply happy, smile bloomed on Xianyun's face. The smile of an engineer who had been patiently, desperately, waiting to get back to her true passion.
"Ah, yes," she said, her golden eyes gleaming with a familiar, inventive fire. "The hovercar."
She led him into her workshop, and there, hanging in the air as a shimmering, three-dimensional, and beautifully complex, blueprint of light, was the next stage of their dream.
"This one has not been idle," she explained, her voice full of a quiet, profound pride as she gestured to the intricate, glowing schematics. "While you were… occupied… in Inazuma, this one has been meticulously upgrading the original blueprint. The power-to-weight ratios have been optimized. The steering mechanism has been redesigned for greater stability and responsiveness. And," she added, with a particularly proud, foxy grin, "this one has developed a new, multi-layered, and surprisingly lightweight, alloy for the chassis that should be both incredibly durable and… aesthetically pleasing."
She looked from the magnificent, upgraded blueprint, to the small, brilliant, and now doubly-powerful, boy at her side.
"The plans are ready," she declared, her voice ringing with the pure, unadulterated joy of a creator about to begin her greatest work. "All the theoretical and logistical hurdles have been cleared. All that was missing…" she finished, her warm, proud gaze coming to rest on him, "was my chief engineer. This one has been waiting for you, Ren."