I own Nothing from Game of thrones and Naruto
Dawn of an empire
During the reign of the first man on Westeros the Seven saw the rise of a new kingdom on a continent named Japan learning ahead of the people of Westeros. While the people of Westeros were still how to write and read while Japan was already forming up to be a monster of a opponent with their constant war with each other and their drive to do make everything better. From them making their home and economy prosper to making swords and spear obsolete for front line use making guns and artillery the primary front line use. With their use three clans stood ahead of the others the Uzumaki, Senju against the Uchiha clans that wished to rule all of Japan with a iron fist. To combat the Uchiha threat the Uzumaki and Senju started making allies with the other clans that called Japan home and they were able to form a united front with the Uzumaki leading them against the Uchiha that believed themselves rulers of all they see.
The seven saw Japan as a way to combat the growing darkness in the north with their weapons that can reduce forest to charred wasteland and change the landscape.
So with the seven fearing the growing darkness in the north decided to seal Japan away and wait till a time when they would be needed to fight a enemy that the seven will be unable to handle. So with the Seven talking to Amaterasu and Ame they came to a deal with them were they would release the people of Japan 25 years before any major event would happen. Part of the deal is that Japan will have abounded resource and Fertile lands.
So with the deal struck they sent a holy message to all the monks and priestess in Japan telling them what they had done. And so the seven sealed Japan away at the beginning of Aegon I conquest of Westeros. With Japan being sealed allowed them to concentrate on pushing back the Uchiha. It was a long and bloody war that lasted for 75 years with the Uzumaki and Senju coming out on of it on top with the Uchiha surrendering when they are forced back to their last stronghold in Tsushima. After the war the alliance decide to unite under one flag forming a empire with the Uzumaki being made Emperor of japan and under their leadership Japan prospered.
With the Uchiha beaten into submission the rest of japan can concentrate on advancing themselves so they may be prepared for future threat that Kami has told them about. And so they prepared by advancing their weapons and technology.
And so they waited and prepared till the time came when the seven would release them and have them destroy the darkness.