A/N: Thank you for all the votes! Special thank to @rinatthedisco ^^
The picture above is Shiyuki's father. The italic lines are the things written in the diary.

Shiyuki's POV

I accidentally find my father's diary while I'm cleaning my bookshelf. This is the first time I ever take all of the books out to clean. It's hidden very carefully. On the cover is the Akai emblem with the line "Akai Toji's diary". I curiously open it and read. The first part is all about him and my mother and some other things.

I collected some information about my clan, the Akai. I'll note some basic things about the Akai emblem here.

The upper red part with the word "赤" means Aka, in "赤井" Akai. The lower part, divided into green and blue, refers to our significant eyes. The yellow circle in the middle of the emblem symbolizes our sealed secret technique: "The Revival of Sunflower".

The Revival of Sunflower? What is that? Why haven't I heard of it before?

Here is something I found. I'll note it here.

This is the technique to revive people, passed down within the Akai clan only. Moreover, only the Akai clan can perform this technique. It converts the user's own chakra into life. The longer the subject's been dead, the more chakra is needed. An Akai can only use once in their life.

*Performance conditions:
• The user has enough chakra.
If they don't, not only they fail in reviving the subject, but they also die of running out of chakra.
• Cannot perform on a Reanimated body.
• The subject's body is not rotten, nor destroyed irrecoverably.

*Commonly, the user runs out of chakra as soon as the subject is revived. The number of people surviving after performing this technique so far is under 5. It can be said a life for a life.

*There were so many people of Akai Clan who died meaninglessly since they didn't have enough chakra. The leader of Akai in ancient times thought that they messed up natural laws: Everyone has to experience death. As a result, the Akai had to get retribution for their deed. He begged the Uzumaki Clan to seal this technique up. This well-known technique is a catastrophe. Everyone with this seal has a small "X" on their back, between their shoulder blades.

I'm shocked. If my clan is famous for this secret technique, why do I know nothing about it? Why? Why did my mother hide it from me? No one can give me the answer, so I continue reading.

*How to proceed:
1. The user gets their blood and write the word "復" - "re" in "revive" (復活) on the subject's chest, on the place of heart.
2. Hand Seal.
Monkey - Rat - Horse - Ram - Bird - Dragon - Ram - Dog - Ox - Tiger - Hare.
3. Releasing chakra.
The user's chakra is released, forming a huge yellow vortex, which looks like a sunflower. That's why this technique is called "The Revival of Sunflower".
4. After getting enough chakra, the user forms the "Tiger" seal to turn chakra into life.
5. The life will go into the subject's body through the word "復", forming a scar and revive the subject.

***

In my opinion, this is an excellent technique. Why did they seal it? Wasn't it created so that people wouldn't suffer from losing their loved one? This seal is hereditary. The Uzumaki had to put a seal on everybody that time. The children born later in Akai Clan have this seal, as their parent's gene is tied with it. I want to restore this amazing technique, so I'll go to the Uzumaki remnants to find out how to undo it.

At the moment, there are not many Akai left, only around 4 or 5 families. No one of us can perform this technique.

...

I found the solution, but I learned that it's dangerous to do so. I can die if I dare to unlock the seal. But so what? Nothing can stop me. The other Akais said that I'm crazy and kept away from me. They see this technique as a calamity, after all. No one cooperates with me, so I'll do it on my new-born daughter Shiyuki.

The diary ends here. I put it down, shocked. I sit there astonished for a long moment. I understand now...

The other Akais keep away from me because they think that I'm crazy just like my father. My mother sneaked away whenever I asked about my father because she was mad at him. He was so risky, and he was why the rest of Akai Clan turned their back to us. And the reason why he died right after I was born... Because he tried to undo the seal. Did he succeed?

Oh right, "the small red "X" between their shoulder blades". I quickly grab several mirrors. I try to look at my back. No! No "X"! He made it?! I'm able to proceed with the secret technique of my Akai Clan?!

I'm depressed immediately. Who will I perform it on? The first one to pop in my mind is Neji-kun. No, I don't think Neji-kun will die. So who? I don't even know. I definitely don't have enough chakra to revive anyone.
Wait, the Byakugou... Isn't it about storing chakra...?

I have no clue whether I'll proceed with this technique or not. I don't know why, but something tells me to try to achieve Byakugou. It says that I will need it.