Reicarnated as a Hyuga in the Warring States Period

Hijiri decided to infiltrate into the secret cave at dawn. He used his usual camouflage technique and senjutsu chakra to hide himself and follow an elder through a secret entrance.

Once inside he went towards his principal objective: the library. He didn't want to simply obtain the seven legendary swords of the mist, he wanted to know how to craft them.

Inside the library, he activated the byakugan to see if there was any trap. There wasn't. It seemed that they were confident that no one would be able to discover this place.

Hijiri took every scroll from the library and put them in a pile. Then he activated his new technique: "Scroll Shadow Clone Jutsu".

With a puff of smoke, another pile of scrolls appeared next to the original one. He took the new pile of scrolls and put them in his storage one.

He then activated the byakugan and started copying the sealing formation pattern of the furnace. It was a very complex work and it took him two hours to copy it. Be careful, to copy it not to understand it.

The next target was the armory where 5 of the 7 future swords of the Mist were kept. Hijiri with his byakugan open scanned the room for traps. He found several seal-based traps that would activate when one of the blades would be taken by an unauthorized person.

Thanks to his knowledge of fuinjutsu, Hijiri was able to deactivate the traps long enough to retrieve the five weapons.

He then left merrily through the front door.

*****

A few weeks later.

Hijiri, in an inn of a city near the one where the Shio Blacksmith clan resided, put down the last scroll.

(Hijiri): 'So that is how they made them. What makes those swords so special isn't only the special materials that are needed but also a blacksmith with the ability to instill his own will in the object. Here they gave the term "to put themself in their work" another meaning altogether.

They use Yin Release to give a sort of sentience to their works so that they can perform extraordinary feats.'

Hijiri also found out that the sealing pattern around the furnace was to create and control high-temperature flames and infuse them with Yang chakra. This made their works extremely resistant to damage.

The only sword that hadn't been forged with the Yang flame was the Executioner's Blade, simply because at that time the sealing formation hadn't been created.

Unfortunately, as it is, this technique didn't bring him tangible benefits. 

After all, he didn't need swords or other weapons. They would hinder him instead of helping.

It wouldn't help the Hyuga clan either, since their style revolved around the Gentle Fist and the byakugan, and these two can't be improved through external tools. 

That didn't mean that the technique was useless to him. Far from it.

It was an extremely precious Yin Release technique. If properly studied and modified it could become a trump card.

It can also be used as a bargaining chip to make deals with other forces. And he already knew who to contact first.