"How's the power of my Fire Release?" Shishou asked.
Obito's face turned pale. It dawned on him that the diminished power of Shishou's Fire Release was entirely due to the lack of air in the base.
Bang! Bang!
Kisame swung his Samehada, breaking the wooden spikes around him. However, for every ten spikes he broke, twenty more rose from the ground, taking their place. Kisame glared at Shishou angrily. His defense against the Flying Thunder God had been turned against him, preventing him from entering the Kamui dimension.
Shishou clearly intended to stall, suffocating Kisame in the base.
The thought of dying from suffocation enraged Kisame. As one of the Seven Ninja Swordsmen of the Mist, such a death was humiliating.
Forming hand seals, Kisame prepared to use a Water Release jutsu. Wood Release would only take up more space around him, hindering Obito from pulling him into the Kamui dimension.
"Water Release: Water Shark Bullet Technique!"
Ten water sharks appeared around Kisame, gnawing at the wooden spikes. Since Kisame's water didn't contain oxygen, he could only exchange the oxygen from the surrounding air to breathe through his gills. But with no oxygen in the air, he used the water sharks to clear the spikes.
However, Shishou continuously generated more wooden spikes, making it impossible to clear them all.
Obito gritted his teeth and lunged at Shishou. Kisame was his ally in the Akatsuki, and if Shishou killed him, Obito would struggle to contend with Nagato.
With the base filled with spikes, the only clear area was around Shishou. To enter the Kamui dimension, Obito had to get there.
Seeing Obito charging, Shishou smiled and continued creating wooden spikes to hinder Kisame.
Hmph!
Obito mentally scoffed, prepared to sacrifice an arm if necessary to use his insertion technique, or even resort to Izanagi to ambush Shishou.
In the next moment, Shishou vanished, reappearing in the space Kisame had just cleared with Samehada.
Shishou reached for Kisame, who blocked with his left hand. Kisame swung Samehada with his right hand, only for Shishou to block and disappear.
Immediately, Kisame tore off the arm Shishou had touched.
Spatial ripples appeared around Kisame as a hand reached out, pulling him into the Kamui dimension.
Obito had taken advantage of Shishou's distraction to enter the Kamui dimension.
"Pant...pant..." Kisame gasped for air, relieved to be alive. The deep-sea shark had nearly suffocated underground.
This base was a lost cause, Obito thought grimly. He couldn't fathom how the Flying Thunder God user had found his secret base.
Glancing at the Four-Tails Jinchūriki bound in the Kamui dimension, Obito turned to Kisame. "Let's go see Pain. We need to eliminate this guy quickly, or the Akatsuki's actions will be severely hindered."
With that, Obito left the Kamui dimension with Kisame, appearing in the cave housing the Gedo Statue. He planned to use the original White Zetsu for Kisame's arm.
Obito retrieved the fully restored White Zetsu from the Gedo Statue and ordered it to assist Kisame. The White Zetsu split off a clone, which disappeared underground.
In Amegakure, the White Zetsu clone appeared at the tower, addressing Pain. "Pain, we were attacked by the Flying Thunder God user..."
Meanwhile...
After Kisame and Obito left, Shishou reappeared in the base, using his Phosphorus Beetles to thoroughly inspect the surroundings.
Finding no hidden White Zetsu, Shishou disappeared briefly, returning with several White Zetsu from his lab.
"Such decisiveness," Shishou chuckled, looking at Kisame's severed arm. When he had touched Kisame earlier, he hadn't used the Phosphorus Beetles but had marked him with the Flying Thunder God seal.
The base was in ruins, with the Sharingan collection mostly destroyed by Shishou's flames.
Controlling the White Zetsu to search the soil around the base, Shishou quickly found what he sought.
Swoosh!
Shishou appeared in a dark chamber. In the center lay a coffin.
Opening it, Shishou saw the remains of the aged Uchiha Madara.
"Madara," Shishou sighed theatrically. "I didn't expect our first meeting to be like this."
Once, he had been a boy dreaming of dancing in the moonlight.
Retrieving his Phosphorus Beetles, Shishou left some of Madara's cells as samples and began devouring the remains.
Devour and feedback!
Madara, having awakened the Rinnegan and reached the Six Paths realm, provided immense energy through the enhanced devour and feedback process.
Shishou's chakra surged, doubling rapidly. His Mangekyō Sharingan's power intensified, his vision growing clearer and brighter.
"The awakening of the Rinnegan is inevitable," Shishou mused, feeling the changes in his eyes.
Madara's Six Paths-level remains had granted Shishou an unexpected boost.
According to the Uchiha stone tablet in the Naka Shrine, the Rinnegan didn't require the Eternal Mangekyō Sharingan, only the Mangekyō Sharingan itself.
The Eternal Mangekyō Sharingan didn't grant new abilities, only durability. Both Madara and Sasuke had awakened the Rinnegan through combining Uchiha and Senju blood.
"Opposing powers, unified, give birth to the ultimate truth—Six Paths power!"
Thus, with his Mangekyō Sharingan, Hashirama's power, and now Madara's Six Paths-level remains, Shishou's awakening of the Rinnegan was certain.
After devouring Madara's remains, Shishou bowed to the coffin and returned to the base.
Finding two surviving Sharingan in a corner, Shishou, seeing nothing else of value, swallowed the White Zetsu he had brought and left.
Returning to his secret lab, Shishou spent a day perusing Madara's scrolls before heading back to Konoha.
Madara's Six Paths-level remains had exceeded Shishou's expectations. His body needed time to adapt to the changes from devouring Madara, making it unsuitable to travel for now.