In the dimension, Rei, Konan, and Tsunade were bathed in the swirling nature energy. Their chakra visible, whirling all around. Even Tsunade who was on the verge of dying from chakra exhaustion, had her chakra stores refilled by the energy of the dimension.
The three chakras leaned on each other and started merging, interweaving. Rei's and Konan's chakra no longer contained only two 'ingredients' but now it was made of three, getting even denser than before, heavier.
Their chakra reserves again rose by the factor of five, far surpassing Kage level reserves.
This time, both Rei and Konan were completely aware of the changes and marveled at them. The previous time, their minds couldn't stay coherent from all the energy but now... they saw what happened and Rei was already devising a seal to 'finalize' the change. For years he was drowning in darkness but now, finally a ray of light enlightened him. He finally knew what he needed to know to finish his binding seal and finalize this bond between them, making it iron-clad! To make their souls regain their form as right now, they were open. He had no idea how to describe it more but it was always there. A weak nagging feeling that something is not right.
They both watched Tsunade... the old woman looking around ninety.
"She is old." Konan frowned and Rei chuckled.
"She is in her late twenties." He commented, making Konan gape at him.
Rei leaned forward and tapped with his free arm on the purple diamond on Tsunade's forehead.
"This is the sole reason she is still alive." He saw Konan tilt her head so he elaborated. "When we connected, she must have been close and a piece of her soul was taken from her."
"Ah! So that's why you were so decisive in connecting with her! She was already a part of us!" Konan exclaimed in great surprise.
"Yes," Rei nodded. "she was not a finalized connection but she was a part of us nevertheless. We just never noticed due to the... small amount of her in us."
"Then? What was the problem?" Konan hummed.
"We took too little of her soul. That would be fine. But we didn't give her any of ours. Her soul was 'leaking' for the lack of a better word."
"Leaking... really?" Konan's lips curled into a small smile.
"I really don't have a better term to explain it." Rei shrugged helplessly. "It manifested in her chakra slowly leaking from her body. Sure, she regenerated it but it put a tremendous strain on her body and life force." Rei lovingly put his hand on Tsunade's cheek. "Day by day, she must have felt herself dying but even her lifelong medical experience couldn't save her."
"That's... shuddering thought." Konan bitterly grimaced and decided to be good to Tsunade.
"Her body couldn't keep it up and she was slowly starting to be unable to regenerate her chakra. She herself must have recognized she was dying. It must have taken years." Rei caressed Tsunade's cheek. "She would be dead years ago if not for her stored reserves in the yin seal."
"I see. She was lucky."
"More like dead tired most of the time." Rei snorted as he put his thumb under Tsunade's eye and gently rubbed it, removing a thick layer of make-up. Under Tsunade's eye was a deep black circle. One, a certain future Ichibi Jinchuuriki would be proud of. "Well... it also took a considerable amount of life force from her since there was nothing else holding her body together. She is a Senju. Senju would have her current look if he was around 150-180 years old. You can understand why I freaked out in the tavern."
Konan nodded. To think the woman who was barely thirty lost around a hundred and fifty years' worth of life force. Konan really couldn't help but pity her. She didn' know how much of that is the new bond and how much is her own sincerity but... it didn't matter. The bond was a part of her and she decided to accept it wholeheartedly.
"Oh, finally." Rei smiled as he saw Tsunade's body reverting. He saw the curious look on Konan so he explained with a chuckle. "Her body is regaining her youth. It is oversaturated with nature energy that is making her younger, giving her back her lost life force. And then, making this life force stronger. The Summoning Animals gained intelligence and speech due to nature energy. They live usually in highly saturated places with this energy and can live hundreds, if not thousands of years..." He trailed off as he noticed the look of understanding in Konan's eyes.
"We are similar to them, then." Konan concluded and Rei nodded.
"Yes. That's my conclusion. Tsunade is going through every change our bodies did when we connected. It is enhancing her all over. Her mind, body, and chakra."
Rei finally took his hand away from the connecting seal as he saw the nature energy around them to calm and settle down. The connection was finished.
"We would have lived for hundreds of years on nature energy alone. But now..." He said as he spread his hand to the sides, gesturing to the dimension of green, tall trees and a thin mist of healthy bright greenish glint, made of nature energy. "Now that we have our own source of an unending energy customized for us?" He turned to Konan with a smugly raised eyebrow and the left side of his lips curled in a smirk.
Konan understood he wanted her to finish the statement.
"We are unaging?" She half-answered, half-asked.
"Oh, we do age. Our souls do. But our bodies will stop at our prime. That's why..." He pointed at Tsunade and Konan's eyes widened. She was now looking like a twenty years old woman, her body strong and toned. Konan noted the woman was extremely beautiful and smiled happily. Yes, this woman would do. She started unconsciously caressing Tsunade's head.
"As long as we have our dimension, we won't age." Konan nodded in understanding.
"Yes... that's why I gotta make more seals in order to improve it and us." Rei chuckled. Konan tilted her head.
"Well, I can finally close our bond on a soul level. That will allow me to root our existences deeply in this dimension and connect it to our souls. Right now it would be dangerous..."
"The Uzumaki seals gave you a lot of knowledge and basis for new theories..." Konan grumbled. She didn't understand and didn't like it when Rei talked about something she didn't understand! But she could only sigh in annoyance.
"That they did." Rei snorted. "Uzumaki forbade soul-level sealing a long time ago. But they kept the knowledge. Most of their sealers couldn't pull it off safely anyway. It almost always ended with some deformities, accidents, or most likely death of the target, so they forbid using it. But with my talent? Hah, I can and will pull it off." Rei rolled his eyes. The knowledge about this kind of sealing was hidden very deeply and discreetly in the sealing scrolls in the Kiri Library. It was not even in one scroll. It was strewn through hundreds of them, most of them useless scrolls that wouldn't see any use. But Rei looked through them all and connected the dots. And he found out the most chilling and exciting art. Sealing on the level far above the grandmaster level. Soul and dimensional sealing.
Creating Dimensions... that always made Uzumaki stumped. They wanted to make their own small world and relocate there. Nobody would threaten them there. But their experimental dimension would ALWAYS collapse so they gave up.
Soul-level sealing... It was one of the most powerful things in the entire Narutoverse. Theoretically, creating Bijuu should be possible if only really, really hard. But in practice? Even Uzumaki couldn't pull it off safely. But Rei could. With enough effort… and time.
And now that he saw and sensed the entire process of connection creation when Tsunade joined... He was sure. He was going to make a soul-level seal. A seal that will allow for far too much than just a simple soulbond. He couldn't help but get excited!