{Hospital, Amegakure}
{5:49 PM, 13th July 13 Yrs ANB}
{3rd Person POV}
"So who's gonna tell me what chakra is made up of?" Ren asked since he had decided that he would teach them all of his medical ninjutsu for a safe haven he needed to start from the basics.
"Uh, Physical and Mental Energy?" Rin asked, what he asked was a very basic question so her puzzled look was warranted.
"Yes, that is correct to the very fundamental level. Chakra is made up of two types of energy, mental energy, and spiritual energy that is produced somewhere in our brain..." Ren pointed to his forehead. "...And Physical energy which is produced in each cell of our body."
Ren spoke getting a nod from every one of them, "So our brain cells are capable of just producing spiritual energy and our physical body is capable of producing physical energy. Their energies are carried through our blood vessels and collect right here..." Ren pointed toward his heart.
"In our heart, these two energies are mixed with each other and create Chakra." Ren finished, he looked at the enlightened eyes of his temporary students and asked, "So if our heart produces the chakra what is the need for all these Tenketsu across all our bodies?" Ren asked.
"They help us form jutsus?" Tadashi replied though his statement sort of turned into a question in the end.
"Of course, they help us use Jutsu, but that was not what their original purpose was it?" Ren asked rhetorically but upon getting no response he nodded. He was reaching anyway, all of this might be basic medical theory but no shinobi needed to know these specifics.
"Alright, Chikara, How do you form a Jutsu?" Ren asked.
"By performing hand seals, each hand seal activates certain Tenketsu along our body, they allow us to use the chakra stored in them to perform the Jutsu," Chikara replied he hadn't really thought about it too much.
The one advantage Ren had growing up was that he didn't have any Jutsu to learn, all he could do was master the academy's three jutsu. Along the way he had learned these little titbits about how chakra works and interacts.
"Good so if you perform a certain Jutsu, how quickly can you reuse the same Jutsu again?" Ren asked. This question made the three Jonin think for a minute.
"The amount of time it takes for the chakra to flow from our heart to the empty Tenketsu!" Rin replied after careful consideration.
"Perfect, now since all chakra must pass through tenketsu, the first Tenketsu where the newly generated chakra is located right here, above the heart..." Ren pointed at his heart.
"The first rule that every medical-nin had to follow was to never mess with this one tenketsu. No matter the damage is done to it, if someone is going to die, then let them die, we do not mess with this Tenketsu okay?" Ren asked, the basic knowledge that he gained also contained brief descriptions of 8 such Tenketsu that were rather special.
Besides them being the chakra centers of the surrounding area, each of them governed something more.
'Maybe if I level up the Mysical palm jutsu to the max limit I'll understand more about it...' Ren thought.
"Alright, now that I have done my duty with the warning, we'll focus on why I asked the question. As Tadashi said, chakra is formed of two different types of energies. The Physical energy and the Spiritual energy. After these two energies have combined and formed chakra, the chakra formed is also made up of two types of energies called?" Ren pointed to Rin.
"Ying and Yang chakra," Rin replied she was the one who was most into the lecture, she enjoyed theory but unfortunately, she was born in the wrong place.
"Correct. Ying and Yang's chakra is fundamentally different from elemental chakra. Is anyone of you a sensor?" Ren asked. All three of them shook their heads but Konan nodded yes.
"Great, I'm a sensor too, now I'm going to focus on sensing my surroundings, you try to sense if you notice something," Ren spoke as he extended his senses actively, his range widened as he could sense about 360m around him.
"I can see that you are actively sensing, your body is releasing some chakra," Konan spoke, her eyes focused on Ren's body.
"Yes, so you see any sensor could detect that someone else was sensing them, the simple reason behind that is she could sense the Yang-natured chakra that my body is expelling in order to extend my range." Ren spoke, he pointed to Chikara and asked, "Why is it so?"
...
"Uhh..." Chikara stammered so Ren turned his eyes to everyone else, after waiting for a minute and getting no answer he nodded and continued, "Because when I extend my senses I actively do it with Yin-type chakra, and the excess Yang nature chakra is expelled from my body."
"Now why was this side tour important?" Ren asked although he knew why he did it it nicely tied up with his plan to make himself seem more valuable. A sensor, medic-nin, and strong combat strength, wasn't I a totally non-disposable asset?
"To show you that Yin natured chakra can pass through physical barriers. If I leave this room, I could still sense you guys through the walls. But if I release a jutsu it would collide with the wall and explode. So chakra can not pass through solid objects, the Yin chakra can, and the Yang chakra can't. With me so far?" Ren asked, getting some hesitant nods from the group.
"Alright, you'll understand more when you learn the mystical palm Jutsu. But before that why did I insist on telling you all about these theories? Because the primary job of the Mystical Palm Jutsu is to break down your chakra into Yin and Yang. The Mystical Palm Jutsu could allow you to heal almost any injury if you master it, but you need to master how to use the jutsu yourself." Ren stopped to take a breath before he continued.
"Just by applying the green glow of chakra on someone's injury doesn't mean the Injury is gonna heal. Do you know the main reason behind the success of Konoha's medical department even after so many years of the development of the medical jutsu, why hasn't the shinobi world figured out the medical ninjutsu yet? Just take Ame for example, how many scrolls of Mystical Palm Ninjtusu are there sitting in your vault, probably more than a dozen..." Ren froze as he realized he was going on a rant.
"Uhmhmm..." he cleared his throat and continued, "Let's take this step by step, first I need you guys to do the chakra control exercise but instead of using the constant flow technique, I need you to use small blasts of chakra to lift the stone up," Ren spoke getting 4 nods.
'I really am a bad teacher, I messed up the whole lecture by going on a tangent about the Tenketsu, the importance of the Tenketu should be discussed after they learn the Mystical Palm Jutsu...' Ren frowned be he leaned back into his chair and focused on his own rock. He opened the skill window once again and focused on seeing his skill level rise... one percentage point at a time.
...
[Rock Cutting Exercise: Lvl 3 (21.32% to Next Lvl)]
[An advanced Wind chakra manipulation exercise that focuses on using wind chakra to cut through solid rock, this skill allows the user better control over their wind chakra and gives their wind chakra a sharper feel.]
[Uses 40 CP per minute]
[+2% to Wind per Level.]
...