Tsunade, admittedly, had a hard time keeping her eyes peeled off of the youth biologically more than 20 years younger given she had aged somewhat in the second war and the youth in front of her had also sped his growth by three years. But despite having hope to recover her youth and the years she lost through continuing her prisoner's search, the fact remained she would be too old to eye the 'youth' in front of him who was a shy away from flashing her entirely.

And what... actually attracted her wasn't the half-naked youth. It was the fact that the ordinarily hyper-excited and perverted youth silently set a seal in the center of her laboratory with an utterly calm expression. Tsunade has had her moments. It wasn't the fact that she didn't like perverts. Despite her 'inexperience', she didn't mind Jiraiya's stare or Dan's attraction back then. Who didn't want to feel wanted?

But her hands just moved when someone tried to be a bit forceful. And when her hands moved, others broke. Jiraiya, after his experience, didn't stop but he clearly 'knew' the dangers and turned tame.

And Dan... last Tsunade heard about him, he had already woken up from the mental shock but wasn't deployed to the force. Even with other medics healing him, he needed a long rehabilitation session to make a full recovery.

Kai, however... had grown on her for two reasons.

These past two months, Tsunade and Kai were practically living together aside from the nights when he returned home and...

Kai would find ways to constantly 'prove' that he wasn't supposed to be expected as anything but a man. The two months were definitely grueling since Tsunade became the only 'mark' in Kai's gaze and ever since he actually became a dragon, his urges practically skyrocketed. And that... earned him a beating. Well, it was either that or actually fighting back and laying ruin to both of their labs.

And when Tsunade's first punch, that Kai just decided to withstand as a form of training, was endured with barely any force through his 'new' body... her 'hell' began then.

Kai... had surpassed her, actually, in durability. She could increase the force of her punch but that did not change the fact that Kai had managed to earn the position of strength that actually allowed him to GUARD her. He was finally her Legacy Guardian and it made Tsunade quite complicated.

But this moment of silence forced her to recall everything that happened over the period of two months.

Kai adopting Sage Transformation, Orochimaru's affiliation, Danzo's captivity, and now this... the way Kai modified the seal was something Tsunade expected from her 'late' Grandmother. Despite her obvious strengths, Tsunade knew her Granny was a massive nerd when it came to seals. She may not have developed the Uzumaki Inheritance but she damn well built it up before passing it on. Her passing memory of her grandfather was actually claiming that Mito is what Tobirama became for the Senju Clan.

While most Uzumaki members are definitely nerds in their own ways, including Kushina who could accurately describe the components of a ramen's flavor, Mito was a little... extreme in her ways. After all, no 'tame' individual would volunteer to seal a devilish fox in her body.

And the youth in front of him was similar. So was Orochimaru.

The type of individuals who knew what they wanted and got it despite the massive political or moral barrier that may stand in their way. As if sensing her gaze, she saw him turn to look in her direction. His gaze was briefly drawn to her form and then her eyes... like usual. If this stare was 'cute' when Kai was actually young then now... she truly was forced out of her views to regard him as an apprentice and a young one at that.

Rolling her eyes at her own thoughts and the youth simultaneously while making sure to clear her head with wine... alone this time since alcohol was making her even more of a risk around him, she remarked with a biting, annoyed tone, "Stop gawking and do your work. I'm not just here to be your chakra battery!"

"But you are convinced that this is better than slowly saving away bits of chakra for years to come, right?" Kai smirked in response.

This is one thing he hadn't understood before.

Tsunade had taught her apprentices the Legacy Technique left by Mito in the Senju Clan— Strength of a Hundred Seals and all of them were talented enough to master it... eventually.

The thing is, that this sealing technique needed a ton load of chakra.

While Tsunade's current chakra capacity was about 260000, nobody knew the actual amount she had 'stored' in that mark of hers. Even if she denied the claim, Tsunade, for all intents and purposes was a chakra battery for whomever that could 'use' her. After all, the Strength of a Hundred Seals stored chakra constantly and supported a Jutsu without the user's conscious effort.

For Tsunade, it was her Body Transformation Jutsu. She could stay young for... well, until she exhausts her chakra.

Kai wanted something else...

Like his basic chakra storage seal, the Strength of a Hundred Seal was a product of Fuinjutsu and Yin Transformation. Unlike other jutsus... Fuinjutsu needed very LITTLE tuning up to be transitioned and usable with Senjutsu Chakra. So little that his trait did not consider a new bit of knowledge at all and thus, had no new skill about it.

But this only made the origin of Fuinjutsu even more mysterious as the seals worked almost too well with Senjutsu Chakra. Orochimaru also devised seals to perfectly transition the Kekkei Genkai of Sage Transformation onto Kai through Fuinjutsu. But Kai wasn't here to dig the mysteries of the world, he wanted to dig something far more crucial.

So, even if Tsunade wouldn't agree that Kai's method of using a 'battery' to form this seal and then run it later was a blatant skip of many steps that actually made Tsunade a beast in the chakra control department, Kai had made it clear that he could still gain the actual benefits of the skill, i.e., 100% chakra control or— 100% Reduction of Chakra Wastage.

If this was before, Tsunade would doubt the boy but since meeting him, her act of not believing the youth has always blown on her face, figuratively.

As such, when Kai sat down in the center of the sealing circle surrounded by inky black scribbles with a large painted spot in the center, Tsunade let out a heavy groan and walked forward before taking a seat not far from him on another painted spot.

It was clear that she did not like being 'passive' but this sensation was just so much more prominent this time given how Kai was intending to use her... still, she stared at the seals. She may not be a Fuin master like Kai or Kushina who was making steady gains in her mastery of seals but she had mastered the Strength of Hundred Seals and this made Tsunade inquire about the most obvious 'flaw' with a frown.

"Why... is the technique's final point of Yin Concentration not fully marked?"

"Because nature energy cannot improve something already considered complete," Kai grinned, "I had to introduce an imperfection to let the nature energy take its course~!"

Understanding the implications of his words, Tsunade's eyes widened, "What?! That almost sounds suic—"

"Awesome, I know," Kai shrugged as he slammed his palms together. Tsunade may have seen the most obvious flaw of the seal but she totally failed to see the minute changes he introduced to Mito's legacy. The remaining few hundred of his clones didn't just sit idle or leave things to luck. They buckled down and did the appropriate research for this seal, noting any possibility that they could and form a plan 'good enough' for Kai because he knew that whether he liked it or not, the contribution of luck despite its necessity is not something that can be controlled.

As such, without Tsunade could complain any further, the seal around them glowed and Tsunade felt her chakra drain and then get refined.

With his knowledge of chakra transfer, refining and absorbing a willing party's chakra was easy enough for Kai. The main point of this whole giant ass seal was to absorb Tsunade's chakra AND introduce nature energy to the mix that interacted with his own chakra signature.

It was almost instant that Kai's body bulked, his underwear stretched further against the confines of his flesh as his muscled, almost 'greyish' body grew even more well-defined while he closed his eyes and stabilized his breath as Tsunade, too, grew silent while she released her seal. The diamond-shaped mark on her forehead inverted and let out thin trails of purple lines over her face that curved around her cheeks while leaving a diamond-shaped space in the center and that's when Kai realized just how much chakra Tsunade had stored...

Millions...

Just too much!

The only thing Kai could compare Tsunade to was what he felt within Mito and Kushina. Make no doubt— Kai never managed to actually measure the beast within them. But, the concept of chakra capacity of such vast and inexhaustible size was... almost 'simple' to Kai for a second.

What use is so much chakra is not used efficiently?

While Genins, Chunins, and even Jonins scrambled over Chakra Capacity— the world of elites is only governed by skill. Tsunade just had the necessary SKILLS to master such a seal and in turn, save so much chakra over the years and not the other way around.

And, Now, Kai let the 'skill' which he expected to be new and thus, have a notification of extrapolation of data marked along...

But it never came.

This skill, this Seal that he wished to form already existed and in written form at that...

[Seal of Adamantine Sage (1/75): Forms a seal of chakra concentration capable of storing Senjutsu Chakra, too, in a special seal which becomes available for use after 5000000 chakra points and senjutsu chakra is stored. Reduces Chakra Wastage by 0.186% at every level. Reduces Senjutsu Chakra Wastage at every level by 0.66%.

Next Level: Store 800978/1000000 chakra/senjutsu chakra or 60 SP]

'Adamantine Sage?' Kai wondered. He knew Toad and the Snake Sage. He considered himself the Dragon Sage. There was a white snake kid but the brat was no sage yet... and he mused if this sage was even alive.

---

Far off, deep within the ocean under a sturdy structure of seals and earth while viewing the formation of a chakra construct entirely red with hints of magma forming around it, a masked, white-clothed maiden sniffed her nose and muttered, "Almost sneezed... is someone plotting against Uzu again? Well, not my problem. Saved them once, they should be one their toes now..." and with a scowl, she turned to view the giant 'phantom', "Damn... I heard that they revive but didn't know it took so long..."

---

Pulling his attention from the name and seeing that the skill had the desired effects, Kai sucked Tsunade wholly off of her chakra without inhibitions. She had a lot of juicy chakra stored in and Kai knew he could manage to grind the skill in one seating.

Of course, this wasn't something Tsunade wanted to experience but she felt that if she could 'satisfy' her guardian with just her chakra... then it would be worth it. Given the initial success of the seal, Tsunade also wished to note the difference between their Seals and if she should even consider... taking up on his offer to practice with him.

And soon, well, in a matter of days, Kai mastered the grind.

[Seal of Adamantine Sage (75/75): Forms a seal of chakra concentration capable of storing Senjutsu Chakra, too, in a special seal which becomes available for use after 5000000 chakra points and senjutsu chakra is stored. Reduces Chakra Wastage by 0.186% at every level. Reduces Senjutsu Chakra Wastage at every level by 0.66%.]

And the most recent addition to the status panel pleased Kai greatly as it opened yet ANOTHER path of improvement.

[Name: Kai

Age: 14

Title: Senju Legacy Guardian

Gamer Traits: Skill Tree; Sleepless Gamer

Rank: Jonin

Hit Points: 100%

Stamina: 100/100% (46.1/min)

Senjutsu/Chakra: 292425 (78800→ 83550+250%) || (2747/min) (785+250%/min)

Physique: 462/1000

Mental: 529/1000

Perception: 404→ 432/1000

Water: 24/100%

Wind: 21.4/100%

Fire: 20.7/100%

Earth: 20.7/100%

Lightning: 20.9/100%

Yin: 40.3/100%

Yang: 40.1/100%]

[Skill points: 2282]

[Reduction of Chakra Wastage: 100%]

[Reduction of Senjutsu Chakra Wastage: 50%]

***

Shoutout to Densys Bratini and Colin Chapman!!

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