The First Research Institute.
It was located in the mountain range at the northeast corner of Sunagakure.
To build this research institute, Sayan ordered an entire mountain to be hollowed out, dispatching 2,000 Doton (Earth Release) shinobi for excavation and reinforcement.
Finally, he put the idle Sasuke back to work, using metal pillars to reinforce the mountain structure again.
It could be said that this mountain was even sturdier than before.
Of course, it wasn't just this one mountain.
Many mountains were already like this.
As the development speed of Sunagakure accelerated, the need for various research sites, training grounds, and advanced factories grew.
However, Sunagakure was built surrounded by mountains.
There wasn't much spare space.
Unlike their big brother Konohagakure next door, who could just chop down a patch of trees to create a new area.
Thus, the mountains that once protected Sunagakure from wind and sand had now become a barrier hindering its development.
So...
Carve out the mountains!
With mountains so large, as long as they could be hollowed out, they would become natural housing with plenty of space inside.
"Kazekage-sama!"
The Sunagakure shinobi guarding the research institute bowed one after another upon seeing Sayan's arrival.
"Mm. Is Shamon-sama inside?"
"Yes, he is."
"Good!"
Sayan then walked inside.
Passing through a curtain of light, Sayan entered.
This light curtain was a type of barrier provided by the Uzumaki Clan. Its function was to identify chakra; only those with registered chakra could enter. If an unknown chakra was detected, they would be blocked outside.
A plaza came into view. At the top of the mountain's inner wall was a massive lamp, emitting light that brightly illuminated the interior of the cave.
Behind the plaza was a C-shaped building.
Or you could say there were three.
Because the First Research Institute primarily studied three different fields.
Namely, Kugutsu (Puppet) Research, Biological Research, and Ninjutsu Research.
They each occupied a building, but the buildings were interconnected. So, you could say it was one building, or you could say it was three.
Currently, Chiyo was the head of Kugutsu, while Shamon was the head of Ninjutsu Research and the overall head of the institute...
"Sensei!"
Shamon, who was immersed in research in his office, heard a voice and looked back. Seeing Sayan's arrival, he put down his work and said with a smile,
"You're back. How was it? Did everything go smoothly this time?"
As Sayan's teacher and the Nidaime Kazekage, Shamon naturally knew what Sayan had gone out for.
After all...
If an accident occurred, Shamon, as the Nidaime Kazekage, was the only one who could maintain order and ensure the village continued to develop according to the plan.
"Yes, everything went smoothly."
After speaking, he activated Sennin Mōdo (Sage Mode). Golden wings appeared at the corners of his eyes. He placed his hand on Shamon's to let him feel the change carefully.
"Good! Very good!"
Looking at the changes on Sayan's face and the surging amount of chakra in his body, Shamon's aged face broke into a wide smile.
"My child, having you is the greatest fortune for Sunagakure."
"The most correct thing I've done in my life was picking you up and raising you."
"Now, my only hope is to see the birth of your three children."
Shamon spoke to Sayan while pulling his hand to sit down together.
"Sensei..."
Looking at his teacher's aged appearance, Sayan couldn't help but feel a pang of sadness.
He had been raised by Shamon, but because he possessed memories of his past life, those two words had never been spoken. As he grew up, calling him 'Sensei' became natural, and Shamon had long since grown accustomed to it.
Although neither said anything, they had long considered each other family.
"Alright, child! It's already a blessing that I could survive the cruel war. Seeing Sunagakure getting better and better, I have no more regrets."
"Sensei..."
"Child, don't try to persuade me anymore. Life, aging, illness, and death are only natural."
"Mm!"
"..."
[You brat, when I told you not to persuade me, you really stopped? Shouldn't you act very sad and ask me if I have any other wishes!]
"Ahem, Sayan, what were you going to say just now?"
"Mm! Sensei, I wanted to say that I can extend your lifespan."
Shamon: "..."
"Then why did you look so sad just now!"
"Well, the atmosphere was just right!"
The two stared at each other, momentarily at a loss for words.
Sayan was the first to speak.
"Besides, Sensei, my Sennin Mōdo can sense a person's life energy. Based on the life energy in your body, you can probably live for another three years, so Sensei..."
"Is the experiment short on money again?!"
Hearing Sayan's blunt words, Shamon felt a bit awkward.
[This kid is still as sharp as ever; I haven't succeeded in tricking him once since he was little.]
"Ahem, it's a little short. Mainly in the area of cloning. You know, everyone's body compatibility is different. Some shinobi have damaged internal organs and need new organs cloned for replacement, but breeding a batch is very expensive. Also, regarding plants, to breed drought-tolerant and alkali-resistant plants, we need generations of optimization. To speed up these steps, we need to buy large quantities of nutrient solution."
"These two are major expenses. If we only had to cover one, it wouldn't be much; we could afford it with the share from the Kugutsu Department's equipment sales. But if it's both together, then it's a bit..."
"So, as long as one of the major expenses can be solved, it'll be fine?" Sayan asked after hearing Shamon's words.
"Uh... yes, but these two things won't be solved anytime soon..."
"Wait for me a moment."
Before Shamon could finish, Sayan disappeared with a Shunshin no Jutsu (Body Flicker Technique).
Soon, Sayan reappeared in front of Shamon.
Only, he was carrying a person wearing a white lab coat.
"Sayan, what are you doing? Quickly let go of Researcher Tobi."
"Exactly, exactly! Let me go already!"
"Sensei, wait a moment."
Seeing Sayan's extremely serious gaze, Shamon, who knew Sayan well, stopped his persuasion and watched Sayan's actions.
"Your name is Tobi, right? You're the one who improved the fertilizer, right?"
"Yes, that's right, it's me. I'm telling you, I'm a senior researcher at the Biological Research Institute. Even if you're the Kazekage, you can't treat me like this."
"Not bad, not bad. I admit no one can beat you when it comes to researching fertilizer."
Hearing Sayan's praise, Tobi, who was being held, lifted his head proudly. But before he could get too arrogant, Sayan's next words followed.
"And your methods of deception and passing off the fake as real are also incredibly sophisticated!"
"I can tell at a glance that you're not human!"
"Ah! Kazekage-sama, how can you insult people! I've shed blood for the Sand! I've performed meritorious service for the Sand! How can you..."
"Bold monster! I'll make you show your true form!"
Dense golden energy surged from Sayan's body into Tobi's.
"Ah~, no~"
Before long, Shamon saw the Tobi being held in Sayan's hand turn into a creature that was white all over with a spiral-shaped face.
"Eh~, ah-re! It's over, I've been discovered!"
Looking at Tobi in his hand, who had reverted to his original form, Sayan said to him,
"Do you have anything else to say?"
"Hehe~, well... will this month's salary still be paid? I have an elderly person at home to support!"
"What do you think?"
"Hehe~, I've performed meritorious service for the Sand!"