Although Ryuga could easily locate the world where Tsukuyomi resided, he was far more interested in watching Tsukasa's outrageous antics. He had no intention of stealing such an entertaining mission for himself.
So, Sougo decided to take Tsukuyomi with him to seek out Tsukasa, while Geiz and Woz remained on the streets, assisting with disaster relief. After all, with the Sky Wall still standing, the villains from the Build world were wreaking havoc across the city.
At the rendezvous point, Tsukasa Kadoya, already waiting, turned to them.
"So? Why did you call me here?"
Tsukuyomi stepped forward. "We need you to take us back to that place from last time."
Tsukasa raised an eyebrow. "You sure? You might see a truth you're not ready for."
"Even so," Sougo said firmly, "we need to see it with our own eyes."
"Very well," Tsukasa replied indifferently, then opened a dimensional wall and stepped through.
Year 2058, Tsukuyomi Family Residence
"Another temporal intruder?" a young Satsuki murmured.
The moment Sougo and Tsukuyomi arrived, the younger version of Tsukuyomi greeted them—by attacking without warning.
Sougo rolled to the side just in time to avoid her strike. "You've been this wild since childhood, huh?"
Young Tsukuyomi's mouth twitched in frustration. "Who are you people?!"
"I'm... you, from eleven years in the future," the older Tsukuyomi explained gently. "Though, admittedly, I've lost my memory."
"Can't you tell by our matching outfits? Looks like you haven't changed clothes in a decade."
"We're not here to meddle with time," Sougo added. "We just want answers."
"What happened in this world?"
Before the younger Tsukuyomi could reply, a young man stepped out of the shadows. He wore a black trench coat and a top hat.
"Swartz?" the older Tsukuyomi gasped, raising her gun instinctively.
"I wouldn't recommend that," the younger Swartz replied calmly. "This world is on the verge of collapse."
"We came to save it!" Sougo declared.
"I intend to save it too," Swartz said flatly. "By destroying all other worlds."
"What?!" Tsukuyomi and Sougo exclaimed in unison.
"If only this world is destined to fall, then none should survive. I'll merge all the worlds into one, and destroy them. That way, this one remains."
"That's monstrous!" Tsukuyomi shouted.
"Coming from someone who pointed a gun at a child?" Swartz sneered. Tsukuyomi hesitated, lowering her weapon.
Sougo took a step forward. "And how do you plan to destroy the other worlds?"
"Simple. Every world has its own Kamen Riders. If I gather all their powers into one vessel, I can merge the worlds into a single reality. Then, I destroy it. Clean, final, perfect."
"So that's why you manipulated me into collecting Ride Watches?" Tsukuyomi demanded.
"I don't need your approval." Swartz grabbed the younger Tsukuyomi's hand. "Come, Alpina."
"Wait," Sougo interjected. "What if your sister turns out stronger than you? Wouldn't she be the one fit to rule?"
Swartz froze. His gaze shifted to the young Alpina.
"Alpina?" he murmured.
"If she's stronger, can't she help you save the world?"
"No!" he snapped, his voice distorted as he transformed into his older form. "That's unacceptable!"
"If she surpasses me," he snarled, "then I'll erase her memories and banish her to another world!"
"Why?!" Tsukuyomi stared at him, horrified.
"Only the strong can rule! And only I can be king!" Swartz roared, unleashing a wave of energy that blasted Sougo and Tsukuyomi through the wall and into the courtyard.
As Swartz charged after them, intent on obliterating anyone in his way, he suddenly found his attack intercepted—not by Sougo, but by Tsukasa.
With a groan of pain, Tsukasa stood tall, bloodied but unwavering.
"No matter where, I'll always protect what matters," he said hoarsely.
"Damn you!" Swartz growled and raised another wave of energy, but just then, Daiki Kaito burst through the dimensional wall, gun in hand, and opened fire to drive him back.
Seeing he couldn't overpower them, Swartz retreated.
Tsukuyomi dropped beside Tsukasa and cradled him in her arms.
"Why... why did you protect me?"
"That's something you'll have to ask him," Ryuga said, stepping forward.
Tsukuyomi looked confused. "You're... going to send me to see him directly?"
Ryuga gave a tired sigh. "You two have the power of time, yet here you are crying over someone's death instead of acting."
He walked to Tsukasa and extended his hand. A golden shimmer enveloped Tsukasa's body. His lifeless form twitched, then began to reverse—wounds sealing, breath returning.
Tsukasa opened his eyes, confused but alert.
"You brought me back?" he asked.
Ryuga nodded. "You owe me a life."
"Yo, Tsukasa, you died once~," Daiki teased.
Tsukasa ignored him and looked directly at Ryuga. "How do you want me to repay you?"
Ryuga smiled slyly. "How about giving me your sister, Sayo Kodaya?"
"Get lost!" Tsukasa snapped, his expression turning murderous.
Ryuga shrugged. "Worth a shot."
"Alright, now that we've got our answers," Ryuga said, "let's return."
He opened a large portal, and they stepped through. All around them, Riders and monsters from every world had begun appearing, turning the battlefield into chaos. Gates and Woz were barely holding the line.
Just then, Sougo felt a strange sensation. He reached into his pocket and pulled out the Grand Zi-O Ride Watch—only to see it crumble into golden dust.
"What the—?!" he exclaimed.
"It's happening more frequently now," Ryuga muttered grimly.
Before Sougo could reply, monsters swarmed them from all sides.
"Hey! Zi-O! Give me back my Ride Watch!" Tsukasa shouted.
Sougo blinked, then tossed the Decade Watch to him.
[De-De-De-Decade!]
The Decadriver appeared on Tsukasa's waist, and with practiced ease, he inserted the watch.
"Transform!"
[KamenRide! Decade!]
Daiki watched in shock. "Wait, I thought your Rider powers were gone?"
"They were," Tsukasa said. "But I stored half my power inside the watch... dozens of chapters ago."
"See that?" Ryuga laughed, patting Sougo on the back. "He only used half his power to beat you so badly!"
Sougo: "..."
Some things are better left unsaid.