Training field 0 (Kamui's P.O.V.)
Standing in the training field, a young eight-year-old girl with shoulder-length silvery-white hair and an amethyst sharingan was thinking about the coming training. She had a sleeveless black kimono top and black shinobi pants. Around her waist was a white sash.
'Today's the day I learn the Uchiha Clan's famous jutsu, the fireball jutsu. The fireball may be basic, but from what I've read, it's useful for shinobi of all levels. It'll be a great jutsu that I'll be able to use when I graduate.' She was really excited at the prospect of learning such a useful technique. 'Before I go though, I should calm my mind. Dad always says that the best thing to do when your anxious or overly excited is to calm your mind and meditate. I guess it's time to try it.'
Sitting down, Kamui began to center her mind. Her thoughts coming to a halt as a pulse of chakra spread from her core to the rest of her body.
'What's this?' her eyebrows raised.
She was confused. She had always felt like her chakra was a little different from the norm based on how her father explained it to her, but this was the most overt indication to date. Focusing on her core, her body jolted as her consciousness was pulled into her mindscape, her vision faded to black.
Kamui's mindscape (Kamui's P.O.V.)
A few moments later, Kamui's eyes shot open. She jumped to her feet only to find something she never would have expected.
In front of her was a paradise. Around her was a garden of a large assortment of plants of different colors. The predominant color she could point out was the silvery white that colored the water. She noticed that there were flashes of seven different colors flashing through the silvery white river. Looking further, she could see an ocean in the background of the same type of water, but it seemed to be covered in a haze of fog that obscured it from view.
"It's nice to finally meet you" She quickly turned around, assuming a fighting stance, to find a young woman in front of her. The woman looked like an older version of herself.
"Who are you? Why am I here? How am I here?" Shocked, Kamui started firing off questions in rapid sequence. She would normally be pretty calm about surprises, but this was on a different level than anything she had ever experienced.
Shaking her head, the woman looked at her. "Calm down I'm here to help you" She said with a kind and peaceful manner.
Looking at her peaceful demeanor, Kamui started to relax her stance, but kept her eyes on the older woman.
"To start off, I am you, or at least I am a being who's sole mission is to train you to be the best version of you before merging with you and leaving you with the full inheritance of your predecessor." The young woman said clinically.
"What do you mean. Who was this predecessor? How are you me and not me?" Kamui asked. Truthfully, this was very confusing.
"Your predecessor was the rightful successor to a divine position in another realm." The young woman started with a calm, but somber tone. "As a result of a situation that would very likely lead to her death, she cast her divine core into the void using a sacrificial technique. It ripped her body and soul apart leaving her essence to bond with a compatible person. That was you. Her will descended into you in the form of a silvery white marble. Her initial purpose was to groom you for the first twenty years of your life before merging with you. However, something happened that changed those plans." She paused. "Your birth father volunteered you to contain the nine-tailed fox to save the village."
At those words, Kamui raised an eyebrow. It wouldn't be a stretch considering the odd situation that was her joint custody. Having the fourth Hokage as an adopted father was cool and all, but it didn't make sense unless she was an asset to the village whose function didn't originate from the Uchiha clan. Considering tailed beasts were weapons of war that could annihilate villages in one move, it made sense.
"As a consequence, your predecessor used the last of her will to do two things, forcefully destroy the nine-tailed fox's and another chakra source's consciousness and integrate their memories into a single entity. Then, use her own personality as the base for it. That personality is me. Over time, I've integrated into you as more of my chakra becomes your own. While I'm not consciously changing you, part of chakra is one's spirit, so it will whether I like it or not. It's why the containers for tailed beasts tend to adopt some of the personality traits of their beasts. You can't accept another being's chakra without being subject to their influence." The woman finished.
Kamui sighed. She should be angry; she should be furious, but she wasn't. She understood from both her adopted father's and biological father's perspectives on why this needed to happen. They were two members of the village that had to consider its wellbeing. Then there's this being. It was definitely a lot better than the nine-tails would have been if it were inside her. At least it's trying to be friendly. On the other hand, maybe her logical viewing of these different perspectives was the effect of this being's influence. It didn't really matter though.
"Are you a tailed beast now? Can someone forcefully extract you?" She asked. This was an important consideration.
"No, I am merely a sentient part of your own chakra. Even then, we have divine essence mixed into our chakra. Without your soul, they can't integrate it. It doesn't matter how powerful the body is, divine essence is toxic to those who lack the spiritual component. Even if they ripped your arm off and implanted it, they would die from the procedure. Their soul would be the target of the essence's wrath. Either of us would be able to remotely command the part to implode on itself destroying the sample. In fact, It's something I've actively been doing with any parts of your chakra that aren't present inside your body."
"Now onto the initial part of your training. I will be pouring into you the knowledge of your clan's taijutsu and your birth father's understanding of how to transform chakra into the elements. You will still have to practice, but having the knowledge ahead of time will help. Due to the differences in your chakra, I will stick to only transferring knowledge on the basic process for all five elements. I don't want you to limit yourself based on others' limited understanding. Based on my understanding of how chakra behaves, I would like you to explore the different elements yourself. With your massive spiritual strength and divine chakra, mastering the elements will be within reach. This includes the fusion of different elements that would normally be called a bloodline limit. That's the primary ability of your predecessor, elemental mastery. Keep in mind, the basic five will be easy. Once you start combining elements, it'll get a whole lot harder."
Now that got Kamui's attention. Elemental fusion? That was something that would give her enough options to address any situation she'd come across. This thought just led credence to her initial assumption that she was already being influenced. Her thoughts were pragmatic and results oriented, rather than the emotional and attention-seeking nature that would be expected from someone her age.
"Now, that will conclude our initial meeting. I've given you much to think about and I really appreciate you listening without being as angry as you have every right to be." The young woman finished and bowed.
"I think it's only fair. My dad always reminds me to absorb as much information from a situation as possible before taking action. In this case, you've presented a case that at least presents you as a better option than the nine-tailed fox and your story clears up a lot of confusion about me." Kamui said.
"Again, thank you." The young woman continued. "By the way, I would recommend you keep the divine chakra to yourself. It wouldn't do to have people starting to treat us differently. I would also recommend staying away from trying to learn wood release initially. It's too famous and would draw too many eyes. My recommendation would be scorch release. It's something that can be tied to the Uchiha without much trouble, especially with their renown for fire release. This will be a good fusion till you master the individual elements and grow up a little. As you grow stronger, you can use more fusions without endangering yourself too much. Also, ask your father to demonstrate his flying thunder god technique to you and watch with your sharingan active. Focus on the spatial energies used in the process. You will understand why."
Kamui nodded. Honestly, she was glad that Uchiha's had perfect memories or she would have forgotten a lot of this conversation.
As their conversation came to a close, Kamui was pulled into the real world at the sound of her father and Itachi coming to the training ground.