Hearing Shinji's instructions, Mumei didn't hesitate much. As an Uchiha, she held little reverence for dojutsu, other dimensions, or genjutsu. Like Shinji, she was curious about what would happen if 'Tsukuyomi' and 'Jikibi' were fused.
"Here we go!"
With a heads-up, Mumei activated 'Tsukuyomi.'
Instantly, her dark eyes turned crimson, and a tangible surge of mental energy radiated from them, rushing toward Shinji.
Prepared, Shinji didn't resist, allowing Mumei's dojutsu power to invade his spiritual form.
Crack!
With a shattering sound, the entire 'Jikibi Space' seemed to be invaded, showing signs of collapse.
Seated on a stone chair, Shinji surveyed his surroundings.
His 'Jikibi Space' was indeed breaking down, but not due to an inherent flaw—it was a natural rejection response to another dojutsu's intrusion.
This was within Shinji's expectations, so he remained calm.
Mumei, however, grew nervous. "Shinji, should we keep going?"
"We're just getting started!" Shinji smiled. "Don't worry, I've got this. Keep pushing the invasion!"
Reassured by Shinji, Mumei exhaled, then focused entirely on unleashing 'Tsukuyomi.'
Having fused her Eternal Mangekyo Sharingan and successfully integrated the First Hokage's cells through surgery, she had fully mastered the 'Tsukuyomi' and 'Amaterasu' implanted in her by the Uchiha clan, wielding them as naturally as her own awakened dojutsu.
Thus, the 'Tsukuyomi' Mumei cast was of immense power, at the level of an Eternal Mangekyo Sharingan.
Boom!
The rumbling continued as the 'Jikibi Space' kept collapsing. Gales howled, lightning flashed, and even the once-stable stone platform showed cracks.
Staring at the fissures spreading across the round table, Shinji's expression grew serious.
The rejection of 'Tsukuyomi' by the 'Jikibi Space' was fiercer than he'd anticipated. At this rate, the space might collapse entirely.
After weighing his options, Shinji signaled Mumei to stop.
When Mumei halted 'Tsukuyomi,' the collapse of the 'Jikibi Space' ceased, and everything returned to calm.
Mumei quickly asked, "Did we fail?"
Shinji nodded. "Yeah, there's a problem. It seems we can't force a fusion like this."
Mumei said, "Our Mangekyo dojutsu are reflections of our hearts. Forcing two dojutsu to merge would require our hearts to be in perfect sync, right?"
Shinji, deep in thought, frowned at her words. "Unity of hearts…"
There's always a barrier between hearts, even among parents and children or the closest lovers—no exceptions.
So, 'unity of hearts' was inherently impossible!
Unwilling to give up, Shinji began considering solutions.
His first idea was to borrow Mumei's Eternal Mangekyo Sharingan, then use his 'Susanoo Tomoshibi' to wield it, completing the fusion of the dojutsu himself.
But as soon as the thought arose, he spotted a flaw.
'Tsukuyomi' wasn't a dojutsu awakened by Mumei's Eternal Mangekyo—it had been forcibly implanted by the Uchiha clan. Even if Shinji borrowed her eyes, he'd only gain 'Yachihoko,' not 'Tsukuyomi.'
Next, he considered having Mumei use 'Yachihoko' to temporarily transfer 'Tsukuyomi' to him.
But he quickly dismissed this too. Unlike 'Jikibi,' 'Wazunagi,' or 'Susanoo Tomoshibi,' 'Tsukuyomi' wasn't his dojutsu. While Mumei's 'Yachihoko' might temporarily grant him 'Tsukuyomi,' it couldn't be permanent.
His envisioned large-scale immersive genjutsu combat training space required a stable, long-lasting environment. A temporary 'Tsukuyomi' gained through dojutsu power transfer couldn't sustain it.
"Was my plan flawed from the start?"
After pondering without answers, Shinji felt deflated.
The only extreme solution he could think of was to transplant the Uchiha clan's implanted 'Tsukuyomi' from Mumei to himself, then borrow her Eternal Mangekyo containing 'Yachihoko.'
Leaving aside whether Mumei would agree, the practical challenges were immense.
Implanting a Mangekyo dojutsu via a technique was something even Shinji couldn't do. Just researching the theory for such a method would take an unknown amount of time.
"No, that's putting the cart before the horse. I need another way!"
Shinji shook his head, clearing his tangled thoughts.
The purpose of the large-scale immersive genjutsu combat training space was to let Mumei mark Hidden Leaf shinobi undetected, enabling his backup 'Infinite Tsukuyomi' plan.
The essence of this plan was to have Mumei as his trump card, ready to save him if Black Zetsu or other unforeseen threats ambushed him.
Clap!
At that moment, Mumei suddenly clapped her hands. "I've got it! In our glimmerstones, we can see each other's experiences, time spent together, and all our memories. If we're there, doesn't that count as unity of hearts?"
Shinji's eyes lit up. "Right, the glimmerstones!"
The marvel of 'Yachihoko' wasn't just its ability to transfer various forms of chakra—it could also create glimmerstones through marking.
Glimmerstones could be thought of as memory nodes.
For instance, Shinji and Mumei's glimmerstones recorded their entire journey from meeting to bonding, including visuals, sounds, smells, and tactile sensations—all perfectly preserved by 'Yachihoko.'
Mumei had used this feature to record Shinji's 'Jikibi,' 'Wazunagi,' and 'Susanoo Tomoshibi,' enabling her to later return those dojutsu to him.
So, within their glimmerstones, the near-impossible 'unity of hearts' might become much simpler.