'This seems pretty intriguing.'

Izuna curiously looks at the stack of scrolls laid in front of him. ​​

'I always wondered how these bunch of toads gained wisdom and the power to wield Senjutsu.

Chakra is a power exclusive to Otsutsukis. Hagoromo was born with Chakra because of Kaguya. Later he shared his chakra with the rest of beings through the use of Ninshu.

Chakra became a privilege accessible to all living beings on Shinobi World. But Senjutsu was present way before Chakra, since Gamamaru trained Hagoromo in Senjutsu.

Now, here is the question. How come these toads came to know about Senjutsu? Maybe these scrolls might answer my doubts.'

Izuna grabbed a scroll to read it.

"This is…"

The writing of the Scroll surprises him.

"These markings! They are similar to the one present in 'Grimoire of Sin'. Is it a coincidence of some kind?"

Izuna turns towards Fukasaku and questions him,

"Fukasaku-san, where did you get these scrolls? I have never seen this writing anywhere? They look so ancient and I can sense a vast amount of Nature energy in them."

Fukasaku contemplates for a while before he replies,

"Izuna-boy, these scrolls are a heritage of us Frogs. Many millennia ago, one of our ancestors saved the life of a certain 'Person'.

The 'Person' was seriously injured and was on the verge of death. At that time, there was no concept of Chakra or Senjutsu.

The ancestor together with other animals nursed him back to health. It was that 'Person' who taught us the concept of Senjutsu and trained our ancestors in Senjutsu together with other animals.

He created Mount Myoboku, Shikkotsu Forest, and The Ryuuchi Cave. These places later turned into the 'Sage Regions' of the Shinobi World.

These scrolls were written by him to pass to his inheritor. Though I am still unaware of his possession which he passed down. Even Great Toad Sage doesn't know much about this.

There is no record of that person's information in the remains of history. As far as I know, he fought against some otherworldly invaders and died in the battle.

There are still some ruins of their battle spread throughout the Shinobi world, though the exact location of these ruins is unknown. This is the information passed down by our ancestors." Fukasaku explains to Izuna.

'Really, there was such a backstory. If I remember correctly, none of the Otsutsuki demonstrated 'Senjutsu' in any battle. Well, their chakra is potent enough on its own.

Like literally, they can reincarnate themselves through the use of 'Kãma Seals'. Also, they convert the entire life energy and Nature energy of the planet into fruit and harvest it. So why do they even need Senjutsu?

This can only mean one thing, Senjutsu is a power not inherited from the Otsutsuki clan but its source is the same as this 'Sin Seal'. The person whom I fought against wasn't an Otsutsuki, He utilized a power similar to this 'Sin Seal' and he didn't have any sort of Dojutsu.

Now, if he is like Otsutsukis, then I highly doubt I killed him during our previous encounter. So who is he? Why was he after the 'Sin Seal'? And most of all, what is the origin of Senjutsu and Fuinjutsu?'

The gears in Izuna's brain churned and various questions popped up in his mind.

'Let me see the content of this scroll first. Maybe they could answer some of my questions.'

Izuna opens the scroll and activates his Sharingan to decipher it. He looks at the scroll's content again but couldn't decipher it.

'I have to use my Mangekyo Sharingan to decipher it.'

He turns towards Fukasaku and informs him,

"I will borrow these scrolls for a while. I think I will be able to decipher them."

"You can do as you please, Izuna-boy. I will return. Maa would be waiting for me." Fukasaku hops away from the spot.

Izuna teleports from his spot. He reappears at the top of the giant tree in Shikkotsu Forest.

'Let me try to decipher it now.'

He activates his Mangekyo Sharingan and inspects the scroll again.

'WELP! I still can't read it.'

The 'Sin Seal' reacts again and forms strange markings around his right eye.

The contents of the scroll reveal itself to him as some information pops out in his brain.

----------

Day 27,

It has been a while since I got stranded in this dimension. There are various inferior creatures in this dimension. They can't utilize any sort of energy, and their mortality rate is very high.

A bunch of low-level animals saved me, and I feel thankful to them. Well, not really! But still, they saved my life.

The fight with the Otsutsuki clan members left me with many serious injuries. I have to open a Yomotsu Hirasaka to escape from the chase of Otsutsuki clan members.

But they were prepared. They even brought Karasuki and Hirasuki to chase me down. The Time and Space artifacts helped them chase me down to this dimension.

It requires lots of energy to travel freely through dimensions, but thankfully our clan techniques are oriented towards space-time and sealing.

These Otsutsuki spent lots of their Chakra to travel through space and time. It will be awhile before they recover and search for me.

I have to get help from natives of this dimension. Sigh… again, these animals have very low intelligence. I should teach them one of my clan's techniques.

Maybe these animals could gather their surrounding energy and attain some spiritual wisdom. I need help while dealing with those Otsutsukis, and even if it is a little, it will suffice.

So, I trained them in Senjutsu Arts; the energy utilizing technique of our clan. Otsutsukis are born with Chakra and thus they have a natural advantage against us, but their nefarious ways of gaining power didn't sit well with us.

Sigh… I am caught in such a difficult situation."

The writing on the scroll ends. Izuna rolls the scroll and contemplates.

'This scroll is nothing more than a diary. But it seems like I will get all of my answers in them.

So, my hunch was correct. Somebody taught these toads, slugs, and other summons. And from the looks of it, he was chased down by Otsutsuki clan members.

Man! These Otsutsukis are present everywhere. I always wondered how Kaguya had enough time to create some ruins in the Shinobi world when she was busy with her 'Peaceful World Quest'.

Looks like Otsutsuki visited Shinobi World earlier on an expedition to hunt this guy down. They even took the Time Artifact Karasuki with them.'

Izuna takes out a piece of strange metal in his hand.

'If my guess is correct, then this broken artifact of the Namikaze clan is Hirasuki, as mentioned in this diary scroll. Maybe it broke during their final confrontation and during later years Namikaze clan chanced upon it.

But to think, there are other races out there who are as equally powerful as Otsutsukis. Looks like I am born in an alternate or parallel Naruto World.

I have to make preparations for this new danger too. There are other powerful beings out there with their sight on 'Shinobi World'. I need as many helping hands as possible.

I have to talk with Tsunade regarding her Sage Mode training. She will be a great asset in the future. I have to pay a visit to the village and check on Shisui and Itachi too.

It has been a year since I left the village. I only briefly return to the village just to show my face to Mom. All this training had exhausted me mentally, I have to take a break and in the meantime convince Tsunade too.'

Izuna stows away the scroll and jumps down from the tree. He senses the chakra of Katsuyu and moves towards her.

"Lady Katsuyu, I will fulfill my promise now. In a few more days, I will bring Tsunade to Shikkotsu Forest for Sage Mode Training."

"Thank you so much, Izuna-kun. I will be able to keep the legacy of Kenshiro-sama alive this way. His clan got annihilated a few years ago, but thankfully I will be able to pass his legacy to Tsunade. Only if that girl Tsunade found a mate and birthed a child. Sigh…" Katsuyu sighs and her optical tentacles twirls around.

"Farewell, Lady Katsuyu." Izuna teleports away from Shikkotsu Forest.

"If only you were a bit older, Izuna-kun. Then it would have worked out…"

Katsuyu sighs again and looks towards the temple.

------------------------

A/N:- Here is my take on this part. I won't write the entire entry of diary scrolls in one chapter because I don't want to collect enough hate in one chapter. We will build it up gradually and so I will write these diary entries throughout the story to make it more natural.

Also, comment if you like this idea and want more of such Origin story.