Kingdom of Rōran.
"Woah, Yasu, this place really is beautiful, the architecture is amazing! Look at the all the lighting." The towers seen in the Naruto movie didn't exist at this time, but the city was still mesmerizing.
"I know, didn't I tell you? Hey, there's a good-looking inn over there, let's get a room."
"Alright, I wanna see if the drinks here are really as good as you said, let's also get some chicken while we're at it." Tsunade couldn't wait to try some local delicacies, besides gambling, what she loved most was eating and drinking.
"You're gonna bankrupt us in this trip, Tsuna. But believe me, the liquor here is actually supposed to be great." Ieyasu didn't have to make that up, it was just true.
After eating their meal and drinking, Tsunade went to sleep in their room.
On the other hand, Ieyasu got into exploration mode.
To be honest, he could see a massive underground sea of chakra right under his feet with the Byaku-Sharingan.
It was so dense it almost felt like it was alive, and maybe in some way, it was. After all, chakra is the energy of life, the combination of spiritual and physical energy—or at least it was the way humans produced it.
Ieyasu had his theories for the origin of the Ryumyaku: it could truly be some sort of primordial energy, it could be some sort of residual energy from some ancient Otsutsuki ritual or some other alien relic, it could also be something naturally formed throughout years of accumulation through some weird mechanism—maybe it's a relic of an extinct civilization that once roamed this Earth.
Either way, what he was happy about is that there seemed to be zero traces of souls in the Ryumyaku, meaning it wasn't an actual living being like Tailed Beasts.
Now, all he needed to do was slowly absorb it, and honestly, he could probably survive swimming in it. 'What would it taste like?'
'No! Let's play it safe, I'm definitely not the type of guy to do stupid shit on impulse. I'll either scam the queen or break in directly. I don't believe the bloodline restriction can stop me, it's not like I want to use it normally.'
Ieyasu made his way to the royal palace of Rōran, which was built over the Source of the Ryumyaku.
As a ninja, there was no reason to not sneak in, so he did just that.
After scanning the building with his Byaku-Sharingan, Ieyasu finally found a silhouette that looked like royalty—it was the young Queen Seramu, Sara's mother.
...
Queen Seramu was sitting on her throne listening to the last reports of the day.
Nothing out of the ordinary had happened recently, Rōran was a small kingdom after all.
The last piece of information she received today was about a young pair of a man in sunglasses and a blonde woman coming into the kingdom.
The person that made the report simply mentioned they seemed somehow noteworthy, even though they could quite say why.
'It seems they're really not busy enough, what's noteworthy even supposed to mean? Aren't you just randomly reporting anything at this point? Well, at least this ociosity means that the kingdom is doing well.' Queen Seramu thought.
Even after everyone else had left the room, Seramu still sat there, staring at the throne room.
When Seramu was finally about to leave and go to her chambers, she suddenly saw a young man wearing sunglasses hanging from the ceiling with his hands.
"Yo, greetings Queen Seramu, please don't scream, I swear I'm a good guy." Ieyasu didn't expect to be noticed so soon, he got distracted with the beautiful architecture of the palace and ended up walking into the Queen's line of sight.
And yes, Ieyasu liked to be like Spider-Man sometimes, hanging from the ceiling on all fours or with his hands—he had even practiced how to use chakra threads as webs.
"Wh- who are you? How did you get in here? Are you a Shinobi from Suna? What's your business here? We have nothing of interest to Suna here!" Seramu wasn't too panicked since she could see the intruder was clumsy, but she was still very worried about his real intentions.
"Actually, I came here for two reasons. One is to warn you to never open your Ryumyaku for anyone, it'd be best if you just sealed it forever as it would be very dangerous if put in the wrong hands."
Seramu was surprised this guy knew about the Ryumyaku, it was a royal secret. But she still asked, "I understand, I wouldn't be so careless, what's the second reason?"
"Actually, you would be so careless, don't you know yourself? I only said this because my prophecy said you would open the Ryumyaku for a person with bad intentions. The second reason for me to be here is that I want to be the one to seal the Ryumyaku, how does that sound? I can guarantee no one else will ever be able to harvest it's power for evil."
"How do you plan to seal it? And I'm the only one that can open it anyway, why do I need your help?" Seramu instinctively felt like this guy was a scammer.
"Look, Your Majesty, I'm just asking, but do you think I'd be saying all of this if I couldn't even access the Ryumyaku without you?" Ieyasu thought it was a matter of just mentioning it, 'Wasn't this queen easily fooled in the movie? Is that creepy puppet master more trustworthy than me or am I just bad at looking legitimate?'
"Do you mean to say you're here to take the Ryumyaku?"
"Yes, and look, what I said is true, you guys don't even use it. All it does is make you a target for evildoers, I meant it when I said you're going to be targeted by someone in the future."
"Do you think I'm a fool? And if you're so capable, why would you be here convincing me?" Seramu didn't really understand this man's behavior.
"Huh, you're right! Maybe you really are a good Queen! I shouldn't have considered talking in the first place, why should I settle for inefficient methods like asking for permission properly? This isn't sex, there's no need for consent when I'm doing a good deed as long as my fists speak the loudest."
"How shameless! And do you truly think a single Shinobi is enough to deal with Rōran?"
When he heard that, Ieyasu used Flying Raijin to look cooler and teleported behind Seramu, holding a blade to her neck. "Look, let's just play nice, you don't do anything, I take the Ryumyaku and leave, everyone's happy. I'll even leave behind a smaller version of the Ryumyaku that can be used as a generator. Isn't that a good thing for Rōran? I'm fully capable of taking you guys on, so consider carefully."
'A good thing for Rōran? Well... if he isn't lying, maybe he's right. And now I really can't do much to resist.' The Queen thought.
"Fine, then follow me, if you can do as you say and make a usable generator, I'll even thank you. No one in all the generations of Rōran rulers could properly harness this power for the kingdom." Seramu was more of an optimist than a fool, she just had bad luck in putting her trust on that shady guy from the movie.
The Kingdom of Rōran actually had historically great nobles, it's almost like it's in their genes to be kind. That's probably why something or someone made them the administrators for the Ryumyaku, or maybe the Ryumyaku authority is what changes their personality.
Either way, other bloodlines have inherited traits like this, so it's not a stretch that their ancestor must have been an Asura/Hashirama type.
It took the pair nearly half an hour just to reach the actual Source of the Ryumyaku.
When he got there, Ieyasu realized this place was even more chakra dense than he imagined—it was like staring at the surface of the Sun with his Byaku-Sharingan.
'If I can absorb and integrate with this, I'll have similar chakra levels to Kaguya with the Ten-Tails. For all intents and purposes, it's endless.' Ieyasu forced himself to not grin widely or drool in front of royalty.
The actual source was an underground room with a dome-shaped roof covering a cifcular pool of purple chakra.
In the middle of the pool, a sort of tower was built to manage the flow of the Ryumyaku, this tower island was connected from the middle to the outside by a bridge.
'I wonder what determines chakra color, it's probably not a big deal since the anime made it all light blue when it wasn't a Susanoo or Tailed Beast.'
"Your Majesty, I'll need about two hours to make the seals needed to leave behind a perpetual generator, is that a problem?" After some thought, Ieyasu felt like it'd be too much of a scumbag move to just steal it even if they weren't using it and it was truly just a vulnerability to the Kingdom.
"It's fine." Seramu felt like this thief was a bit too shameless, she was clearly about to get off work, this was obviously occupying her limited free time. 'If he truly makes the Ryumyaku useful for the people, it really won't be a problem.'
'I mean, all I need is a fancy Earth Release container with the right seals and openings to act as a reactor, then I just need to seal the minimum amount of chakra to create perpetuity.' Ieyasu had studied all information he could find on this, apparently, chakra was quite scientific, there was a certain figure of chakra density that made it turn into what's essentially a perpetual chakra generator.
It's almost like the point in which a certain amount of gas is dense enough to form a star.
All he needed to do was create a dense enough source for the container.
...
Around two hours later.
"Phew. It's done, Your Majesty. Now, do you know what happens if one hypothetically dives into the Ryumyaku itself?" Ieyasu wasn't sure if you'd just melt or explode, or if maybe something weird happened.
"Please don't kill yourself here. And to answer your question, first of all, any human, Shinobi or not, would definitely die."
"As for how that happens, my family records say that the Ryumyaku often manifest unstable space-time phenomena upon contact. What is known for sure is that it's very unstable, it's so energy dense that it's akin to lava, and it also disrupts space-time in some way. We really don't know much more."
"Please don't be reckless, it could cause unexpected damage to the Kingdom. Just don't harm the people, please." Seramu was worried this lunatic would actually jump after she saw the defiant look on his face.
"Don't worry, miss, I'm a professional."
'If it's about space-time disruption, can't I just spread Flying Raijin seals all around the room and the Ryumyaku itself? And the Eight Trigrams seal should be able to store it after I teleport it there. Considering it probably has no will, it shouldn't immediately kill me or do anything major with a small amount, so my Hashirama-boosted Adaptive Vital Body should be able to handle it over time.'
"In case, hold this Kunai, it's important in case the space-time disruption is excessive."
After saying that, Ieyasu...
"YOU ACTUALLY DIVED IN?!" Seramu lost her cool on the spot.