Reisen Riou's injuries healed before reaching home, shrugging off the embarrassment of being carried—though, honestly, he savored Ei's softness. Damn pride. That night, he invited her to optimize Longevity Thunder Elixir Art. He was eager to integrate Electro and Cryo Regisvine properties, enhancing both the elixir and his barrier, now tied to it. Used to setbacks, he bounced back fast.
Ei, who'd trained in the elixir, joined his research for the first time. Her speed stunned him. In under 90 minutes, she absorbed his findings—properties, evolutions—and optimized structures and algorithms in 30 more, boosting healing. Using one material sample, she fully parsed Pyro, Cryo, and Electro Regisvine properties, handing them to a numb Reisen Riou as he tweaked his algorithms. "Here's your Electro-simulated data," she said casually, oblivious to his shock. A supercomputer would've taken a month.
"Studying a god's brain might be next," he muttered, inputting her data into Resurrection's supercomputer, syncing his will to balance the properties with his elixir. As he worked, eyes closed, Ei didn't tinker with her odd experiments. Instead, she propped her face, watching him, blushing at some thought.
The Cryo Regisvine, gone mad, bashed the execution field's ground. Reisen Riou ignored it; Ei's face darkened. The Pyro Regisvine, trembling, dragged the Electro Regisvine into playing statue. Ei stormed the field, knocked the Cryo Regisvine out cold, and left. Resurrection scrambled to save the valuable specimen. Ei, mood soured, dove into elixir research.
The elixir's Electro-simulated healing and buffs had limits: material-free casting reduced potency, but with materials, it triggered Spell Maximization, amplifying effects. Take Narukami Ring Seal: maidens used it for minor wounds without materials, but for severe injuries, Narukami Grass as a medium boosted results, or as a consumable, fully activated, it healed near-fatal wounds. A recent case—a Hatamoto with four arrow wounds, seven slashes, two spear piercings, and elemental damage—was saved by a skilled maiden using two Narukami Grass stalks.
Two months later, at Reisen Riou's estate, his domain unfolded silently. His body shifted subtly, mind racing, Laws of Longevity and Transformation weaving within from his elixir work. Images of anatomical studies and enemy kills flashed, birthing an Annihilation Law's aura, mingling with the others. The Precision Law, tied to Death and Reason, eluded him—no aura formed. He realized it perfected his archery, ensuring no shot missed within range, a sublimation of his bow skills.
Ei, arms crossed, stood conflicted in his courtyard as his domain pulsed. "It's begun," she sighed, relieved. His body burst, but prepared, companion attire materialized. Expressionless, he gazed skyward as a golden fifth star descended:
5th Star: Practice – Grants an Electro shield with Thunder Spear Array, +10% movement/attack speed; converts theory to experience rapidly.
It salvaged his melee weakness, turning knowledge into mastery. Not flashy, but transformative for a theory-heavy, talent-light youkai like him. "Try it," Ei urged, eyes gleaming.
"Gulp. Maybe Anko?" he hedged.
"She's too weak. Your barrier ends her," Ei dismissed. Anko's truth stung—barriers favored the underdog, especially peers. (Ei totally wasn't securing her "household status.")
"Go easy," he pleaded, knowing her style. His unnamed barrier lasted longer, withstanding one serious flat attack before Ei's Electro slash cut it like tofu. The elixir-barrier resonance—near-identical to the elixir's structure—amplified both strength and backlash. Without his Great Youkai resilience, he'd have fainted. Sprawled, he groaned, "No ultimates, just flat attacks."
"No ultimates like Anko's?" Ei teased, disappointed.
"All flat attacks," he sighed. His system leaned on Precision and Annihilation for sustained damage, with rapid-fire and Thunder Spear Array for single or group combat. Ultimates, condensing mastery into explosive bursts, weren't his style but had uses—like Ei's Musou no Hitotachi, which slew Orobaxi, a non-Archon felling a god.
"Ahem, Ei, I'm a Great Youkai now," he said, heart racing. "Ready?"
"Cough!" Ei choked, flustered. "Talk to Sister." She tried to bolt, but his LV8 Flowing Light Escape, 20% faster, caught her hand, pulling her into a hug.
"This softness… this curve…" As he leaned closer, smack—he hit the ground. "Ow, Ei, too harsh!"
"You pushed it," she huffed, adjusting her clothes—no black stockings, just thin war boots.
"Couldn't help it," he grinned, ogling her legs. Ei smirked, reading his scheming face—smooth moves, cooked rice, still plotting despite the fall. A millennia-old novice, she'd eaten more sweets than he'd had meals; no tricking her.
Bones cracking back into place, he stood. "Let's see Makoto—er, Sister Makoto." Ei vanished faster. Smirking, he knew she was trapped—he'd tipped Makoto off yesterday.
At Tenshukaku, he bowed. "Greetings, Lady Makoto."
"So eager," she teased.
He chuckled, silent. "Approved," she said. "When's the celebration? No wedding, but we need a feast."
"I've got ingredients ready," he said. Makoto sent Torachiyo to fetch Saiguu and Miko, leaving the oni general to cover paperwork—riddled with errors. Reisen Riou fixed them swiftly, archiving as Makoto, Saiguu, Ei (with Miko napping on her head), and Anko arrived. Teased, Ei stiffened robotically, brain crashing as he led her.
In his cave heaven—(readers might've forgotten this)—prepared since their confession, Inazuma-style maple and Narukami wood manor housed preserved sweets, meats, premium mushrooms, and vegetables. Reisen Riou, cooking solo for the special occasion, whipped up 30 portions of desserts and dishes in half an hour while they chatted, easing Ei.
"I entrust Ei to you," Makoto said solemnly.
"I'll cherish her, Sister," he beamed. His cooking rivaled Inazuma's top chefs, bolstered by Ritou's rising culinary stars. Ei, relaxed, devoured 20 portions of sweets. "No fried tofu?" Saiguu griped.
"Tomorrow, Lady Saiguu," he laughed. He'd skipped fried tofu—more snack than dish, needing sauces. Saiguu, promised her fix, left with Makoto and others, Reisen Riou ejecting them via cave heaven disk, leaving Ei (steaming), a sleeping Miko, and him inching closer.
"Ei…"
"Put Miko out first!"
"She's sound asleep."
Next dawn, before roosters crowed, Reisen Riou rose, refreshed yet aching. "No wonder Sister said wait till Great Youkai," he groaned, recalling last night. His elixir-fueled endurance barely tamed Teyvat's fiercest thunder. Preparing tonic sweets and Saiguu's fried tofu, he smirked, ready for more.