(POV Tsunade)
It was unnatural in fact as I had done a deep scan of his body when I got a chance and his entire form was perfect. I don't mean like he was just healthy but that there was not a single cell or organ in his body not operating with absolute efficiency. Brain was perfectly shaped to learn and retain massive amounts of information in a short frame of time. I had only seen a brain like this in members of the Hyuga and Uchiha clans whose dojutsu causes sensory overload without this sort of shape.-
The rest of his body was no different as his skin, muscles and bones are denser than normal by a lot and even his blood is the universal O negative and absolutely PACKED with vitality. My clan was the only people i have ever seen with vitality like this which allowed us to heal faster and live longer than normal shinobi but only my grandfathers vitality was anywhere close to this extreme. Oddly though Kenzo's hyper dense body was perfectly balanced with this vitality so that he only healed about as fast as an above average member of my clan.-
If his body didn't need so much vitality to heal at that speed I am willing to bet he'd be practically unkillable. Stabbed through the heart? Healed a split second later. Decapitated? It'd take hours for his body to stop functioning properly and even longer for his brain to die. Not that I think anyone was capable of inflicting fatal wounds on him to begin with if he chose to run away as his speed was so fast that it reminded me of the Raikages. His physical strength was also not far from his speed as he matched me of all people.-
My body was strengthened to an extreme degree using a special seal I created called the strength of a hundred that makes my physical strength inhuman. The slightest exertion from me could break bones and my full power could create craters and an eleven year old matched that without any special technique. Even more terrifying was that I noticed that his strength was growing as his body did. I was worried that by the time he turned fifteen his raw force would be enough to wipeout squadrons of Jonin soldiers from the air pressure alone.-
The only normal thing about the boy was that he was inexperienced and needed guidance to learn something. I had even seen him show a flaw in the form of his short attention span. Well that probably isn't entirely accurate as it wasn't that he had a short attention span so much as his senses were so sharp that even the slightest sound or light caused his mind to immediately focus on it. It was almost like paranoia was built into the very essence of his being as he did it purely on instinct so much so that I almost thought he truly had a short attention span.-
I helped him train out this instinctual habit of his since it was the only thing stopping him from excelling at Iryonin jutsu. He did open up to me after discovering my fear of blood and told me something that was listed in his file but horribly incorrect, he is a sensor but not the normal sort. His form of the ability was unaffected by the seals designed to keep out the normal sensors and as a result he had to experience the death of an entire clan.-
That knowledge alone made me worried about his metal state as the way he described it was much like those sensory nin posted on the battlefield during a fierce battle and none of them were alright after experiencing that. There was something about feeling dozens of lives getting snuffed out in an instant that left the sensors broken or at the very least shook to a great degree. Hearing a child no more than seven or eight went through such an experience and didn't receive help for it made me concerned. Unlike myself though Kenzo didn't let his trauma drag him down.-
He harnessed it to motivate himself to learn and push himself forward and admittedly his drive and conviction infected me a little. I had began trying to break the hold my fear held over me and it was hard but the boy was supportive and helpful in his own way. It was small things really, he'd bring food or make a stupid joke to distract me if I started to feel overwhelmed. the sort of stuff no one would normally notice but I picked up on easily due to experience dealing with Jiraiya who did the same thing constantly.-
It was the same reason why I knew he lied to me about when I asked him where he vanished to after I summoned Katsuyu. Just like Jiraiya the boy had the same tells in that he tried to distract with smiles, laughter or body movement when he lied. If I didn't know Jiraiya like I did I would have never noticed it myself as he was that good at deception. Another thing that didn't add up was that the one thing Kenzo was obsessed with is beasts with the stronger the better yet he fled away from Katsuyu like she was the bane of his existence.-
Perhaps he sensed something from her that made him uncomfortable but in that case I simply had no clue what it could be. Katsuyu held a special place in the animal kingdom after all as she was both many and one, weak and powerful, complex and simple. Kenzo was more in tune with the way of beasts than anyone I had ever known so there was no telling what he discovered from her and I wasn't going to ask. Everyone had their secrets and if he felt like keeping this one all asking would accomplish would be to make him clam up.-
I moved on from that event without much fuss and oversaw his taijutsu and iryonin jutsu training since he had already completely mastered the alchemical knowledge I could teach him. It was all supplementary knowledge and theories with some techniques for crafting medicine so it was no surprise he picked it up easily. I forbade Shizune from telling him just how fast he was growing as a medical shinobi but I can say with certainty that his skills rivaled a special jonin level Iryonin at worse and surpassed them in some aspects at best. -
His mystic palm was monstrously powerful and could heal a broken bone in no more than five minutes. Such a feat of healing rivaled my own and for good reason as it takes an extreme amount of precision and large quantity and quality of chakra. It was on his record that he possesses a vast reservoir of chakra but to witness it in person is a very different thing than reading about it. The insane part was that I had met Jinchuriki with less chakra than he has. The Jinchuriki of the three tails, Yagura for example had less chakra than Kenzo so long as he didn't tap into the three tails within him.