Almost an hour after Uehara went to sleep, Sakura successfully opened the second path of death. As dutiful as always, Chizuki woke Uehara up. Although he was groggy from the nap, he managed to completely wake up after Chizuki fed him a bit of her blood.
As of right now, Sakura was still sitting underneath the same tree while Uehara was in front of her.
"Since you've opened the second path, it's due time I teach you about chakra."
"YES!"
Uehara slightly winced in pain as he decreased the sensitivity of his hearing to that of an elderly human.
[I forgot how loud she can get.]
Chizuki giggled from the vantage point of a branch she was sitting on.
[This is the Sakura I know.]
Sakura instantly simmered down when she saw how Uehara's shoulders had suddenly tensed up.
"Hehehe…"
She lowered her head slightly.
"Sorry, Black-sama. My mistake."
Uehara didn't bother acknowledging her apology. He instead opted to continue his lesson.
"As I was saying, chakra consists of the four main elements in the following order. Air, water, earth and fire. Air restrains water, water restrains earth, earth restrains fire and fire restrains air. That is how the cycle works. There's also the fact that water restrains fire and earth restrains air.
Sakura nodded with enthusiasm.
"Mm!"
Uehara continued.
"Right now, you are naturally attuned to fire. This doesn't mean that you can't learn other elements. It just means you have more talent in training your fire aspect of chakra. I've already taught you the basics so now I'll go into the advanced theoretical segment. I'll go in the formal order so I'll first give you a summary of each element, starting with air."
A cluster of wind condensed around Uehara's hand to the point that it could be vaguely seen with the naked eye.
"Wind is the most free of all elements. Wind is mostly used by nomads and sailors. You control the wind, you can control momentum and direction and pressure. The last person you want to fight is a master of wind. If they lighten the air pressure around you, you cannot breathe and they may cause your body to explode. There are also more applications like controlling the momentum of a person. Everyone faces a certain amount of wind resistance. Remove or add to that resistance and you can control their momentum. If you're also skilful enough, you can also use the wind to change the direction of any attack. It is similar to the vortex of flame you used to redirect my flame bullets."
A look of understanding dawned on Sakura.
"Oh, I get it now!"
"Good. Now, let me explain water."
The sphere of air was now replaced by a sphere of clear water.
"Water is the most malleable and most versatile element of the four. It can mimic the properties of air and earth in the forms of mist and ice respectively. Water is also present in every mortal life-form, whether it be in the form of blood or juices. A master of water can use the water in your body to control you. A master of water can form ice stronger than metal. If you learn the concepts of wind and fire, you can also control temperature to a degree. Water can also be used to heal so after masters of earth, water users are the most durable. Water may not be the strongest element, but it is the most versatile and is greatly loved by assassins and alchemists."
A look of concern appeared on Sakura's face.
"Um, Black-sama? Will it be harder for me to learn how to use water chakra?"
"Naturally."
"Oh…"
A look of determination appeared on her face.
"Then please teach me well, Black-sama!"
Uehara closed his eyes as he winced from Sakura's loud voice. Taking a moment to orient himself, he acted like nothing happened and continued with his lesson. The sphere of water was no replaced by a lump of earth.
"Earth is unanimously, the most destructive and also has the strongest defense. The weakness of that is, it is not as versatile as the other elements, much easier to defend against and it is much harder to see results in the beginning stages of training in it. But if you can persevere, it is possible to reach a level of strength where you can level an entire city with a stomp of your foot. The element of earth is preferred by merchants and farmers for reasons I'm sure you can derive. Earth is after all, needed to sustain life."
The lump of earth was now replaced by a bright orb of fire. Instantly, Sakura's eyes brightened up as she wanted to hear about her element.
"Fire is the most chaotic element. Remember the following sentence that I say. Fire consumes to survive and spread. Amongst all the four elements, fire ranks first in chaos and is also the hardest element to control. An advantage of fire is that you can use it anywhere since fire comes from within. A single spark of life essence and some chakra will result in a blazing fire. That's why fire is the most loved element amongst soldiers since it is harder to restrict the element of fire. Although in nature, fire can be snuffed out quite easily, but with a person's will and chakra acting as the spark, fuel and air, it is quite hard to contend against a master of fire."
The next words were said in a somewhat tired tone.
"As a consequence, fire-element users are usually hot-headed and are quick to anger while being a little slow in the head. A single spark and they'll burn an entire city."
Sakura pouted in indignation. Uehara ignored Sakura and looked over at Chizuki.
"Come. This next part will also concern you since I haven't told either of you yet."
"Yes master."
She landed gracefully on the ground and then instantly appeared next to Sakura in the seiza1 position.
(A/N: [1]. Japanese method of sitting where a person sits in a kneeling position. Treated as the formal/traditional way of sitting.)
Sakura snorted before she changed her posture into the seiza position from her previous lotus position.
Uehara calmly waited for them to sit properly before continuing.
"I've already told the both of you about the four elements numerous times but there's somethings I haven't told you. Besides the four basic elements, there are also two conceptual elements. They are the elements of light and darkness. The reason why I say they are conceptual is they encompass a broad spectrum of certain things. Darkness is associated with death and despair while Light is associated with life and love. You could also refer to these two elements as Yin and Yang. They're opposites of each other and can fundamentally be classified as negative and positive energy."
He waited a while for them to show understanding before carrying on.
"Let me explain darkness first. I'll refer to it as the element of yin since it is the term you two are most familiar with. Almost anything non-physical or ethereal and cannot be affected through normal means is associated with yin. So your ghosts are yin. Illusion techniques are yin-related since they affect the mind and soul. Anything that is not classified as living or not of the living world is almost certainly yin-related. If any techniques you use are meant to target your enemy's mental fortitude or soul, it is mostly yin-related. But that doesn't mean yin is evil. It is because you humans don't understand it that you classify it as evil. Without yin, you wouldn't be able to function since yin is also your soul."
He then looked at them to see if he could detect any confusion in their eyes. He was glad to see both of them understood, especially Sakura. After opening the second path, her understanding over death helped her understand what Uehara was saying about the element of darkness.
"Now, I'll go into the element of light. I'll refer to the element of light as yang. The yang element is classified as anything that is living or anything that belongs to the world of the living. The reason your mind and soul can be carried over after you die is because they're yin. Yet if all you had was a mind and soul, you wouldn't be able to exist in the world of the living for long. That is why you need a physical body, which is yang-related because it can allow you to exist in the living world with minimal difficulties. Physical bodies are made from a combination of all four elements which are yang-related, and then a soul will come in to reside in the body, giving it life. Techniques which use any attacks of the four basic elements as well as the element of light are yang-related since they target the physical body."
He lifted both hands to chest level and when he opened his palms, there was a sphere of darkness on one palm and a sphere of golden-white radiance. Both of them were very small, only having a radius of five-centimetres.
"These two spheres contain the elements of light on one hand and of darkness on the other hand. Both are equal in every aspect, whether it be size or attack power. I'm going to show you something that will help you understand the next part I'm about to explain."
He then slowly began bringing them together. When there was only five-centimetres remaining between the two spheres, there was already a reaction as they began to vibrate considerably. Uehara kept his hands in the same position and began to speak.
"The area of influence or the domains of these two spheres have met and are battling for supremacy."
He noticed the slight confusion in their eyes and so chose to explain.
"Let me explain what an area of influence is. Imagine a candle. If you put your hand close enough to it, you will feel it burn. Although you are not touching the candle flame itself, you are within its area of influence for its elemental aspect of 'heat'. If I create a giant fireball in the air, although you are a hundred-metres away from it, you will feel hot. That will be because you are within its area of influence for its elemental aspect of heat. The same is happening here. These domains of these two spheres of darkness and light have collided. Now, I want you to watch what happens next."
As he pushed his palms closer together, there was more of a reaction between the two colliding opposite forces. But it didn't take long before the sphere of darkness started to slowly lose its mass. The eyes of the two girls widened at the phenomenon and so, Uehara chose to explain.
"Although these two opposing elements are the same in every aspect, the light element, or in this case, the yang element, has an advantage since we are currently in the world of the living. There's yang all around us and since the element of yin is more closely associated to non-living, it has a distinct disadvantage when fighting against the yang element in this region filled with life. It's the same as an equal amount of equally trained soldiers fighting against one another, but one side having a fortress."
The sphere of darkness finally dissipated while the sphere of light remained vibrant, but had a distinct decrease in size.
Before the girls could ask any questions, he silenced them.
"First soak up what I told you. You'll then have proper questions to ask me in the future. ."
Sakura replied respectfully.
"Yes, Black-sama."
Uehara's mouth twitched.
[That doesn't sound right if she says it like that.]
He walked up to Sakura and patted her head.
"Call me Aoki. You've proved your strength and that you're someone I can acknowledge. So call me by my surname of Aoki."
Sakura became dazed for a while before a smile slowly started spreading on her face.
"Yes, Aoki-sama!"
Uehara closed his eyes as he winced. He then removed his hand from her head with a burst of speed and flicked her forehead thrice, resulting in a series of cries.
"You're-Too-Loud."