Inside the Northern Base, a cold silence filled the air like falling snow. Artoria, Rin, Kay, Ogami, and Sophia all stood within the chamber filled with bookshelves.
"The civilians should've come back after we defeated the monster," Rin said, her brows drawn tight in frustration. "But why haven't they…?"
Ogami's fist slammed onto a metal table with a metallic clang. "Forgive me, Sora! I failed you!"
Rin hesitated for a moment, then stepped forward. "This must be hard for you, Ogami-san."
He turned sharply, eyes stormy and filled with grief. "Don't talk like you understand. None of you do. A parent's greatest treasure is their child! Sora is… my everything!"
"Ogami-san…" Artoria stepped forward. Her voice was soft but firm. "I promise—I'll bring Sora back."
Kay glanced over at her, a flicker of worry in his eyes.
Ogami stared at Artoria in disbelief, then narrowed his eyes.
"Is that all you're good for? Promises?" he growled, stepping closer.
Before anyone could react, he grabbed her by the collar of her school uniform, yanking her forward.
"Didn't you say you made a promise to Sora? Well, where is he now?! Answer me!"
"Mr. Ogami-san, please—!" Rin stepped forward in defense, but Artoria shot her a quick glance that made her stop.
Ogami's voice cracked. "He's my son… do you have any idea what I'm feeling right now?!"
Artoria stared into his eyes. "No… I don't know how it feels. But I will keep my promise."
Silence fell again.
Up above on the balcony, Sophia watched quietly. Kay and Rin both looked on, unsure what to say.
Ogami finally let go. His hand dropped to his side. Artoria gave a short bow.
Then she turned and walked out.
"Artoria—wait!" Rin called and rushed after her.
{Later, at Artoria's Apartment}
Artoria dug through the bookshelf in the living room while Rin paced behind her.
"We need to figure out what the Hanzaki Megid was based on," Artoria muttered, scanning spines of encyclopedias.
Back at the Northern Base, Ogami and Kay were still inside.
"Artoria has the best intentions," Kay told him. "She might make promises after the fact, but she never makes them lightly."
Ogami crossed his arms, skeptical. "And how does that help me?"
Kay looked straight at him. "Because she knows what it feels like to break one. She doesn't remember what happened ten years ago, but I believe she's still haunted by it. Some promise she couldn't keep… it weighs on her, even now. I know that feeling all too well."
Kay then held out a Wonder Ride Book—Needle Hedgehog.
"Please," he said. "Lend her your strength."
Back at the apartment, Artoria finally found what she was looking for.
"Found it!" she exclaimed, pulling a thick book from the shelf. She handed it to Rin.
"'Amphibian Cryptobranchoidea…'" Rin read aloud. "A Japanese giant salamander. Huh. So he really wasn't a lizard."
"Yeah," Artoria nodded. "This guy's known to regenerate even after being cut in half. It's sometimes called a Hanzaki in folklore."
She held up another book titled The Folktales and Superstitions of Japan: Rivers and Waterside.
"It's written here. The man-eating salamander—said to devour humans and become the king of his kind."
"That explains why Sora and the others didn't return," Rin realized. "Because we didn't destroy him fully. His body… it must've regenerated."
Artoria nodded again. "And remember what he said before?"
"Yes, so the civilians were his prey… to being used as offerings," Rin muttered. "That's awful."
"Then we have to go back. Find where he's hiding them and stop whatever he's planning."
Just then, the door creaked open.
Ogami stepped in.
"What did you promise Sora?" he asked without preamble.
Artoria blinked. "I promised to show him how amazing books can be."
"…Artoria," Rin asked, "why are you so serious about promises?"
"…Artoria," Rin asked, "why are you so serious about promises?"
Artoria hesitated. For a moment, her mind flashed to a blurry memory: a little girl with short platinum blonde hair smiling at her. She couldn't see her clearly—but somehow, the girl reminded her of Morgan.
"…I'm not sure," she admitted. "But what I do know is that… if I have the power to help someone, then I have to use it. That's all."
Ogami stared at her for a long moment. Then, unexpectedly, he chuckled.
"Uhm… did I say something funny?" Artoria tilted her head.
He stepped up beside her, placing the Wonder Ride Book in her hand. "You coming?"
"Hai!" she said quickly, and she and Rin rushed after him, locking the door behind them.
{Elsewhere, Kouh Academy}
The sun was beginning to set.
Issei walked alone down the sidewalk just outside the school gates, stretching and yawning. "Man, what a weird day…"
Something caught his eye.
"Hm?"
There, on the ground, was a blank, white book.
"Huh? What's this?"
He picked it up, inspecting it. "Looks kinda like that thing Artoria has…?"
The book's cover glowed faintly.
"Wait—hold on—"
He opened it and a swirling vortex erupted from its pages and sucked him inside.
At the same time in the other world, the Hanzaki regenerates itself after being destroyed.
"I summon thee… sealed away Megid," Calibur intoned, his voice like steel grinding against stone. "Break free from your chains… and awaken once more."
He opened the book.
CRACK—
Chains within the page violently shattered. A surge of thick black energy erupted like a geyser from the book, spreading into a whirlwind of pages and shadow. From within that chaos, the books came together—binding, fusing, folding—until a figure was born from the darkness.
DESAST!
A monstrous humanoid cloaked in a jagged black-and-red body, his form erratic and constantly pulsing like a creature barely containing its own power. Unlike other Megid, Desast was twisted from all three categories.
Desast crouched behind Calibur, his clawed hand dragging along the floor as he stood slowly. He took a deep breath, and his glowing crimson eyes narrowed.
"…This scent," he murmured. "The world, the books, and the swords… all clashing together again…"
He let out a low, raspy chuckle. "It's a scent both… intensely putrid, like those devils… and amazingly splendid."
Calibur remained still, his sword resting against the ground like a grave marker.
"It's been ten years since you were last set free," he said. "How do you feel?"
Desast paused. He slowly turned his head to Calibur. "…As if I'd ever tell you,"
With no further words, Desast stepped forward and then walked off leaving Calibur.
Artoria, Rin, and Ogami finally made it back to the spot where Sora had vanished earlier—right before being pulled into that other world.
"I thought I smelled something quaint…"
The voice slithered through the air before the three could even move.
From the shadows ahead, a figure stepped forward—lean, jagged, and radiating a dangerous, almost playful malice.
Desast.
"There's a Swordsman of Fire in my midst," he said, grinning as his red eyes locked onto Ogami.
Ogami's jaw tightened. "It's you… Desast."
"Some things never change," Desast chuckled. "Still playing with these toys, I'm guessing?" He reached into his side and pulled out a crimson Wonder Ride Book, turning it in his clawed fingers like a trophy.
"He has a Wonder Ride Book!? But how—?" Rin's eyes narrowed sharply.
Ogami didn't look away from Desast. "Souvenirs… from the swordsmen he's killed in the past," he said grimly.
Artoria's eyes hardened. She stepped forward, holding out Jackun to Domamenoki toward Ogami. "It's me he's after. You two go on ahead—save Sora."
But Ogami's mind flashed back to Kay's quiet words earlier, his warning still echoing. He shook his head.
"No." He took the book from her, his voice low and steady. "This guy's all mine." Without another word, he tossed Needle Hedgehog to Artoria.
"I'll leave Sora to you kids."
He planted his feet, gripping the Dogouken Gekido in both hands. With a snap, he opened Genbu Shinwa.
Genbu Shinwa!
He slammed it into the Gekido Shelf, the massive sword's mechanism locking the book in place. In his mind's eye, he was transported into a vast library encased in stone, towering rock formations around him like guardians. Pulling the trigger, he summoned a massive turtle-shell-like wall of stone.
Genbu Shinwa!
"Henshin!"
With a roar, Ogami swung down in a crushing vertical slash—shattering the stone wall as it burst into armor that wrapped around his frame.
Cleave with one stroke! Divide the lands!
The rocky visor slid into place.
Rumble! Rumble!
Gekido, the sword of quakes!
Now Kamen Rider Buster, Ogami leveled his massive blade toward Desast. "Still gotta keep that promise of yours, right?" he said, his voice muffled but resolute through the helmet.
Artoria clenched her fists. "I will! Let's go, Rin-san!"
"We'll leave you to it," Rin nodded, turning toward the portal. The two ran forward and leapt into the rippling book-gate, vanishing into the other world.
Behind them, Buster's blade met Desast's claws in a clash that sent a shockwave through the clearing. The two combatants locked eyes, neither yielding.
From a shadowed corner of the ruins, Calibur watched… saying nothing.
Meanwhile, in the other world…
Sora floated within a shimmering bubble, one of many trapped in the towering "bibles" Hanzaki used to keep his prey suspended. The distorted echoes of panic and crying filled the air as the other captives writhed helplessly inside their own prisons.
"…Father…" Sora whispered, curling his knees to his chest.
Suddenly, a loud scream echoed above—and something crashed into one of the bubbles with a dull thump.
"OW! That fucking hurts!" the newcomer groaned, rubbing his back. The bubble wobbled violently before settling.
Inside was a teenager with messy hair and a scowl—Issei.
He blinked, scanning his strange surroundings, until his gaze landed on the small boy staring at him from the neighboring sphere.
"…Hey, kid. You okay?" Issei asked.
Sora nodded hesitantly. "You… you're not with the Salamander?"
Issei snorted. "Hell no. Name's Issei. And you are?"
"…Sora."
"Come on... work!" Issei gritted his teeth, struggling to awaken his Sacred Gear. A faint green glow flickered around his arm, and suddenly a red gauntlet materialized, emitting a thin beam of green light that shot toward the sky—but just as quickly, the light vanished.
"Yes! I did it!" Issei exclaimed, pumping his fist in triumph. He swung his arm to punch the bubble trapping him, but instead of breaking free, he bounced off and landed hard on his backside. The red gauntlet faded away.
"Aw, man!" he groaned, rubbing his back.
Not far away, Artoria and Rin spotted the flicker of green light piercing the sky from a distance.
"What was that power? Looks pretty weak, though," Rin remarked, narrowing her eyes.
"We should check it out," Artoria said, her voice quiet but determined. Deep inside, something stirred — a faint resonance like a missing part of herself responding to the signal.
Back in the real world, Ogami swung his sword at Desast, but the Megid leapt clean over the strike and sliced fiercely at Ogami's torso before flipping through the air and clashing swords again.
"Man, that stings!" Ogami muttered, stumbling back under the force.
"Getting rusty, old man?" Desast taunted, a cruel smile twisting his lips.
"It's been ten years! Cut me some slack!" Ogami retorted, sending a burst of orange energy streaking toward Desast. The Megid dodged nimbly and charged forward. They launched themselves into the air, blades colliding with a thunderous shockwave.
Meanwhile, trapped inside the other world, Issei groaned in frustration as he hit the ground again.
"Ugh, why won't this Sacred Gear cooperate?!" he yelled.
Sora, curled up and hugging his knees, whispered quietly, "I wish I never opened that book… Books are the worst. I miss my dad."
Issei's expression softened as he glanced over. "Hey, it's okay. Someone will come for us. Don't lose hope."
Suddenly, a voice called out.
"Sora! And... Issei?!"
Both boys looked up to see Artoria and Rin sprinting toward them.
"Artoria and Rin?!" Issei blinked, surprised.
"We're here to save you," Rin said with a smirk. "Just didn't expect to find a pervert like you trapped here."
She flipped open her Wonder Ride Book.
Lion Senki!
Water erupted from the book, blasting the translucent bubbles and shattering the prisons. The trapped humans were freed, their cheers echoing.
"We're free!" "Thank goodness!" The crowd's joy was cut short when the Hanzaki Megid charged in, scattering the people with a terrifying roar.
Issei quickly grabbed Sora, pulling him close.
The Hanzaki Megid snarled, "The King's food... You will pay for this!" His eyes burned with fury as he faced Artoria and Rin.
Rin wiped sweat from her brow. "Guess you were right, Artoria. It did regenerate."
"Let's finish this fast," Artoria said. "Issei, keep Sora safe, okay? I promised I'd bring him back to his dad."
Issei nodded, though still unsure of what was really happening. "Got it!" He held Sora close, staying just far enough to watch the fight.
Rin opened both her Wonder Ride Books.
Lion Senki!
Peter Fantasista!
Artoria matched her with her own.
Brave Dragon!
Needle Hedgehog! Despite all odds, the beast with a thousand sharp needles survives the jungle's harsh trials.
They slid their Wonder Ride Books into their swordrivers.
Rin was transported to a grand watery library. Towering behind her were massive versions of Lion Senki and Peter Fantasista. She drew her Seiken.
Nagare Battou! The shining Lion Fantasista!
"Henshin!"
Blue mist enveloped her as yellow and green sparks coiled around her left side.
Roar and Sparkle! The claws of fantasy now reside within the blue swordsman!
Meanwhile, Artoria appeared in a library ablaze with swirling flames. Giant versions of Brave Dragon and Needle Hedgehog loomed behind her as she drew her Seiken.
Rekka Battou!
She slashed twice in an 'X' formation. A fiery dragon roared to life from the Brave Dragon book while glowing green needles circled her.
"Henshin!"
When the power of two books combine, the sacred sword is infused with strength!
WONDER RIDER!
Artoria transformed into her new form: Dragon Hedgehog.
Honing the blade with the power of two attributes!