Konoha

In the most famous building of Konoha, the Hokage building, an old man was sitting on a chair with loads of paperwork and reports on his desk that needed his reviews and signatures. Even though he was currently the most powerful and respected person in the whole village, the only feelings on his face were immense sadness and tiredness. With a smoking pipe in his mouth, Hiruzen Sarutobi was staring out of the window at the 4th Hokage monument.

Konoha suffered the most losses of any village in the 3rd Great Ninja War due to having to fight every village. And merely a year later, they had to face another assault from the rampage of the nine-tailed beast, which not only killed the 4th Hokage but also a lot of their ninjas and civilians. This not only increased the burden on him and the existing ninjas but also caused Konoha's orphanage to be overpopulated. Hiruzen sighed again, finally starting his day by getting that damned paperwork done.

Normally, an orphanage will have fifty to sixty children every year in Konoha, but due to the following incident, not only did the existing orphanages become full, but many new orphanages had to be opened to meet the demand.

In one of these orphanages, Senju Kaida, a 5-year-old orphan, was being treated because he got into a fight with some older boys who were badmouthing his parents and sustained a significant head injury.

After being treated by a medical ninja, Kaida Senju woke up with an intense headache, thinking, "Damn, what is with this headache? As a patient of Chronic Regional Pain Syndrome, I am quite familiar with pain throughout my body, but this headache seems different. It's not just some external pain but something internal."

Slowly, he opened his eyes and looked around, frowning upon noticing the unfamiliar surroundings. "What is this? Where am I? This is not the hospital room I am familiar with." With his memories all jumbled up, Kaida was confused about everything around his situation when he noticed, "Why are my hands so small? Wait, why am I so much smaller? Did I somehow return to the past?"

But his train of thought broke when a middle-aged man entered the room. He sat beside Kaida and asked, "Kaida, are you alright?"

"Who are you, sir? And why are you calling me Kaida?" Feeling more confused, Kaida asked the man.

The man replied in a worried voice, "Oh! I think the injury has caused some memory loss. Don't you remember anything, Kaida?"

After hearing the question, Kaida tried to remember more about the name, trying to recall if he had heard it in his life. That's when his headache intensified, and he passed out again. The old man became worried and quickly called the medical ninja again, but after inspection, the ninja said, "Since he is so young, I think the injury on his head has made him lose some of his memories. There is a chance that they will come back after one or two weeks, or they may never come back. But his physical condition is good, so there is no need to worry."

"Thank God he is not in danger. And about memories, it's a good thing that he lost them. Since he lost both his parents during the nine-tail rampage, all those memories were mostly painful ones. Now he can make some new and happy memories for himself."

The old man was the caretaker of the orphanage. As a retired ninja, he could have lived a simple, carefree life, but he decided to start this orphanage all by himself. Since he was just a chunin during his career, his assets were not much. Even so, he decided to start this orphanage, as he was also an orphan and knew how important a simple shelter is for a child.

As for Kaida, he especially cared for this child because he was indebted to his parents. They saved his life during the 3rd Great Ninja War. While Kaida pretended to be asleep, he started to gain access to new memories—memories of Kaida Senju. It took five hours to gain clarity, relief from the insufferable headache, and disbelief in his mind.

"Fuck! I transmigrated! And into the fucking Naruto world of all places! But how? I don't even remember dying. Don't you need to die to transmigrate? And damn, transmigrated from that safe world with rules and regulations into this deadly world full of cunning and powerful ninjas. Due to that disease, I always wanted a new life but never in my wildest dream did I imagine having this as my new life."

After a few minutes of disbelief and ranting, he finally calmed down and decided to understand and plan his future. He thought, "All right, I guess I'll be known as Kaida Senju from now on. Unlucky fellow to lose his life to someone transmigrating into him. I wonder how that even works! Anyway, I got a lot of information from his memories. His parents seemed to have died in Kurama's rampage, and he was incredibly lucky to live. And after being admitted into the orphanage, he was examined by Root to see if he could be taken in. Lucky me that they didn't choose him. Hmm, since Kurama's attack took place a year ago, and since he is 5 years old, it seems I'm 4 years older than Naruto and his generation. All right, that gives me more time to train and gain power. The Uchiha massacre should occur in around 7 years, the Konoha crush in 12 years, the Pain attack, and the 4th Great Ninja War in 16 years. Wait, what's this feeling?"

At that moment, he felt a weird energy flowing through him. He thought, "Is this chakra? His memories didn't have anything related to chakra. So does it mean that chakra was unlocked when I transmigrated into him? Finally some good news. With this, getting into the ninja academy should be easier than for other orphans. However, I wonder how my chakra level compares to the chakra level of others. Anyway, probably it is better to get a look at the surroundings first to understand more about this place."

With that, he finally stopped pretending to be asleep and woke up.