Rei connected to the plane of the seal and the very first thing he saw was... nothing. This obviously surprised him. 'So, Hagoromo was not even courteous enough to actually craft a seal space in here?' Rei grimaced, imagining how it would feel to be sealed in a black space of nothingness for well over a thousand years.
Needless to say, he didn't like such a picture. At all.
'This doesn't give me much hope for an intelligent conversation with Kaguya, to be honest.' Rei sighed.
Every seal master who ever studied how to seal entities somewhere knew that crafting a seal space where they would reside was a necessity. It was the very first thing these people learned and for a good reason too! Nobody wanted to seal a bijuu or something of equivalent might only for the entity to go mad in the seal, becoming even more dangerous than before. Even those that hated bijuu wouldn't dare to do this.
Rei really worried about Kaguya's mental state, right about now. Then again, he had hope. She was supposed to be the closest thing to a deity his planet ever saw so... just maybe?
The pocket dimension of the seal was immense and for that, Rei was grateful. Using the moon as the medium for sealing was clearly beneficial in this regard. Thanks to that, Rei wasn't faced with Kaguya upon entering his consciousness into the seal and had time to prepare.
The first thing he did, what any self-respecting and non-suicidal seal master would do, was naturally, check the state of the seal. Surprisingly, the seal was holding up quite well despite its advanced age. Seals, in general, were created to last but keeping something as powerful as Kaguya under a lock for a thousand years... that was a feat on its own considering the average period of time a seal designed to keep a bijuu inside a jinchuuriki was around a century before it started to deteriorate.
Rei quickly discovered why the seal was still working perfectly though. Simply put, Hagoromo disregarded literally everything but durability when it came to the seal. It was obvious he created it on the fly and from what Rei could spot as he let his senses drift through the nothingness of the pocket dimension, it had a lot of rough edges. The entire structure was held together not by the ingenuity of the creator but by the sheer power of his chakra.
The only ingenious part was where the seal separated Kaguya's chakra from her so she couldn't pit her own chakra against the Hagoromo's in the seal, instantly breaking it. Rei couldn't in good conscience give Hagoromo much credit for that though. Anyone with at least one brain cell would do that, knowing Kaguya could just brute force her way out otherwise.
That made Rei's mood rise a bit. A good seal master would be able to escape such a seal. It would take time and effort to find an appropriate way but it was definitely possible. 'Well, that gives me an upper hand in the talks with Kaguya, I guess. Since she is still imprisoned, she probably doesn't have any knowledge about sealing. That's good.' Rei nodded to himself in a pondering manner.
It was then Rei looked at the section where Kaguya's chakra was siphoned and reused to keep the seal going. What he found... made him grimace.
'So she is affected by the Chakra Fruit...' Rei bitterly realized as he watched globs of a black substance being separated from Kaguya's gathered chakra before it was used to power up the seal. 'That might be a problem.'
These globs didn't really exist in Kaguya's chakra. They were just a representation, an image the seal created to portray that Kaguya's chakra was corrupted. Rei reckoned it would be impossible to identify if they were not inside of the seal. The only reason why it was now possible, was that the seal needed pure uncorrupted chakra to power itself up so it automatically separated what it didn't need.
Rei observed the mechanism behind the process and after a few minutes, he decided that he definitely had to use this part to his advantage. Pulling the chakra from within himself, he started feeding it into the seal, knowing it would alert its resident. Rei was not deterred, however. He simply continued tinkering with the seal even after he felt a new pair of eyes intently stare at the back of his head.
Kaguya's presence was unmistakable. The second it engulfed Rei, he could feel her power despite it being sealed. The logical part of Rei knew he had nothing to fear from the woman as she was powerless inside the seal. The primal part, the part governing his nature sensing, however, screamed at him to get away fast.
Standing near her was like being washed over by a tsunami during a hurricane. It was then, Rei understood what Kaguya really meant when she said that all chakra belongs to her. She was a planetary level of monstrosity. The bijuu, artificial or the real ones, simply felt like underdeveloped children compared to her. The only saving grace was that judging by the way Kaguya let her presence freely flow outside of her body without any restraint, she really had no idea how to control it.
Rei couldn't help but quietly chuckle. To him, it seemed the woman staring at him didn't even have a clue about her own power. It was so ridiculous it became hilarious.
'Then again... if she actually learned to control all that energy within herself...' Rei subconsciously gulped, still ceaselessly focusing on altering the chakra purification mechanism in the seal. That brought a new dilemma for him. 'Should I tell her and teach her about her potential or should I simply let her waste it?' Rei really felt conflicted about that. 'Guess it depends on how this will go.' Finishing with his job, the pocket dimension of the seal somewhat brightened as if some kind of previously unseen taint was reduced.
Rei turned towards Kaguya who was furrowing her eyebrows at him, showing him a weird expression as she tried to comprehend why she felt different than a second ago and what exactly changed.
'Quite cute.' Rei revealed a small smirk as the regal-looking woman in front of him looked around like a little confused girl while slightly scrunching her nose. He cleared his throat, getting Kaguya out of her momentary reverie and causing a slight blush to paint her bone-white cheeks before her face again attained that aloof and cold regal look engineered to put a sense of inferiority in those who gazed upon it.
Nevertheless, Rei still found the situation quite funny so the smirk on his face stayed.
They stood opposite to each other, measuring the other with their gaze in total silence while the atmosphere around them was growing progressively more awkward. Rei always knew he would meet this woman somewhere along the line but now that he stood in front of her, he really had nothing to say to her. Jumping at her with his offer seemed a bit too abrupt too so...
As for Kaguya, her situation was even more difficult.
After a while, Kaguya slowly opened her mouth in preparation for speaking but before she could let out a sound, she silently closed it with a disgruntled expression, throwing a ponderingly inquisitive look at Rei who watched her internal turmoil with interest. He really didn't expect their first meeting would go like this.
Screaming, arguing, trying to kill each other while he tried to persuade her of the cleverness of his proposal... yeah, kinda? But, he would never expect having her adorably stare at him in speechlessness.
Finally, Kaguya decided to cut the chase and spoke in a somewhat unsure manner while tilting her head, "Uh, would you believe you are my first guest since I was thrown here?"
Rei really had no idea how to answer that...