Many things in this world have two sides—and Heim's Underworld is no exception.
The golden fruit nurtured within the Heim Underworld Forest possesses the power to elevate a being to godhood. However, this same forest carries a potent corrosive energy. Left unchecked, Heim's Underworld will invade and erode other worlds or planets. If no civilization exists, the corruption is inconsequential. But if one does, it is often doomed to collapse.
Without control, Heim's Underworld spreads its plant life into nearby worlds. These plants require no ideal conditions to grow—once they take root, they flourish rapidly and uncontrollably. The fruits they bear, when consumed by any creature, initiate a horrific transformation: the creature becomes an Inves.
Depending on the individual's attributes and sheer luck, a small percentage may evolve into superior Inves. An even smaller fraction ascend to the rank of Overlord-level Inves—beings of monstrous power.
In truth, the Inves were once the inhabitants of a civilization that fell to Heim's corruption. They are the last, twisted remnants of that lost world.
Now, Earth faces the same grim fate.
Those in the upper echelons of power have long known about this threat, but they've kept it secret to avoid triggering mass panic. The establishment of the World Tree Corporation's Zawame City branch was no coincidence—it was a deliberate move. The spatial barrier between our world and Heim's Underworld is weakest here, making it an ideal testing ground.
Leading the research is none other than Kureshima Takatora, tasked with saving humanity from annihilation.
Their greatest invention: the Sengoku Driver, which converts Heim's fruit into Lockseeds. When equipped with a Lockseed and Driver, a human can extract the fruit's energy to preserve their life—even in a world fully consumed by Heim's plants, without food or sustenance.
There is, however, one last hope: the Golden Fruit.
Whoever consumes the Golden Fruit gains control over Heim's Underworld—its power, its plants, its laws. But this information remains hidden. Only one man, the brilliant but secretive Sengoku Ryoma, has deduced the fruit's existence. Yet he has told no one, not even Takatora.
Instead, Ryoma manipulates others behind the scenes, keeping Takatora in the dark. All Takatora knows is that the forest holds critical secrets—secrets he must uncover.
"It was like this all along?" Takatora was stunned after hearing Ryuga's explanation.
"I told you. If you knew about the Golden Fruit, you'd use it to save humanity. But they don't want saviors—they want gods. That's why you were left in the dark."
Takatora's heart sank.
Ryoma Sengoku held all the cards, and he wasn't alone. Others in the organization were working with him, and without Takatora's research, there would be no way to halt Heim's spread.
Just then, a call crackled through Takatora's earpiece.
"Director! The base is under attack! Dozens of Inves have breached the perimeter—requesting immediate backup!"
Ryuga heard it too, and the two immediately ceased fighting. For Takatora, protecting innocent staff took precedence over any duel. The betrayal came from above—not from the field researchers who remained loyal.
He turned and rushed toward the base.
Ryuga didn't try to stop him. But before Takatora could get far, someone blocked his path.
It was Hase Ryoji, the Armed Rider codenamed Kurokage. Recently defeated several times in the forest, he was still sour from his failures. Mistaking Takatora for a new recruit, he arrogantly challenged him to a "training match."
A pathetic miscalculation.
This was no greenhorn—it was Zangetsu himself, a warrior in no mood for distractions.
Takatora struck once. With full strength, he sliced through Ryoji's Driver, destroying the Lockseed and rendering him unable to transform.
Kurokage collapsed.
But the World Tree's mass production of Drives was already underway. Soon, thousands of Kurokages would replace him—interchangeable soldiers for a war they barely understood.
Takatora rushed past Ryoji without a second glance. Ryugo and Mitsumi, witnessing the scene, carried the unconscious Kurokage back to Zawame City out of compassion.
As for the other Riders, Takatora didn't bother with them. He had only knocked them unconscious, allowing his men to expel them safely from Heim's Underworld. Since they weren't forcibly disarmed, they kept their Lockseeds. Ironically, in this failed sabotage attempt by Sid, the Gaim team walked away with a trove of Lockseeds—and a massive lead on the scoreboard.
But the rankings soon became meaningless.
Heim's Underworld was now eroding deeper into Earth. Cracks were forming even in cities. Through these rifts, Inves emerged and wreaked havoc, killing indiscriminately.
And death wasn't the worst fate.
Those wounded became hosts. The forest's parasitic seeds invaded their wounds, feeding on their bodies to grow more Heim flora.
To the ignorant public, it looked like a deadly virus. Panic ensued.
Street dance crews—once adored for their stylish battles using Lockseeds—were now vilified. No one dared dance publicly anymore.
Almost no one.
One team still did: Team Baron.
Why? Because their leader, Kaito Kumon, didn't care. Anyone who insulted them was met with his terrifying strength. He didn't hurt civilians—but his fierce presence made most people flee before a fight even started.
But his arrogance didn't last.
Oren, hired by World Tree to retrieve rogue Drivers, appeared and swiftly defeated Kaito. It was his seventeenth consecutive loss.
At the same time, Mitsuzane Kureshima, passing nearby, saw Oren—the enemy of all dance crews—and leapt in to help. But he overestimated himself and was captured too. Both were sent straight to the World Tree's detention center.
When Takatora learned that the man he hired had also captured his brother, he was furious.
After a quick investigation, he found out the truth: Mitchy had turned himself in to obtain a Driver. He hadn't been forced—it was his choice.
Takatora suspected Sid's interference again. But now, confused and angry, he sought out the one man who could perhaps clarify things: Ryuga.
To Long, it was absurd.
"Let me get this straight," he said. "Your brother got captured by your own organization, and now you are asking me for help? This world is seriously insane!"