A furore normannorum libera nos domine
We come in large star cruisers and power armor to rape your villages and plunder your women!
I certainly want to flesh out Yamataian culture more.
I have said this before to you, Wes. If you want to flesh it out, you ought to know what kind of influences you're drawing from because mixing and matching from different parts of history and culture could result in contradictions.
In my opinion, the Norse aspect of Yamatai is best as an underlying minority. As Doshii hints, some aspects of it not do well with the general Asian belief of community over individual. However, there must also be said that community did mean a lot to the Norsemen. After all, they were pillaging for gold and treasure because their own farmlands were too meager to support increasingly large communities. So they stole the gold from Christian monasteries to pay for food. And eventually, several groups of them tried to settle in England. See more about the Danelaw and Alfred the Great. It marks the period when England goes from the so-called Dark Ages and towards the more classically-known Medieval period. As a Historian, I acknowledge, the names and dates for these two periods are still open to the same debate of significance.
One major issue with "Japanese" and "Norse" is that both have changed during periods of time. Heian-era Japan would be very different to the Tokugakawa or Kamakura periods. The term Norsemen is derived from the Frankish word for Northmen. Therefore, it actually envelops Danish, Norwegian and Scandinavian cultures. I am no expert on this part of the world but I daresay that to say that they are interchangeable and the same would be a mistake. Therefore, I will use the term Viking, used to describe the fellows who took sail and left their homes (as merchants, raiders, explorers, etc.).
Issues:
Warrior Culture
The presence of a warrior culture is good but by no means are the two the same. In Japan, it was a symbol of social class whilst in most Viking societies, it was something expected from all freemen. I believe the only exceptions were the thralls (slaves) who were supposed to stay behind, obey the women and work the fields.
Combat for the Viking band was the warband, which formed a shieldwall not unlike the Greek phalanx. Once the opposing wall broke, it became a free for all, meaning that the Vikings were good at both unit tactics and a general brawl.
The Japanese
bushi, however, were highly individualistic fighters especially prior to the Sengoku Jidai (whole 'nother kettle of fish in terms of military history). When the Mongolians landed at Hakata Bay in 1274, the Japanese samurai started challenging the Mongolians to a one-on-one duel since that was the way combat was fought between Japanese feudal lords. The Mongolians (as well as their Chinese and Korean levies) did not understand the Japanese nor would they let the duels occur. Instead, they just launched a massive barrage of arrows and explosives shells on the shoreline Japanese and invaded in numbers.
While the second invasion was faced with more sound tactics (fortifications, etc.), those military tactics faded away following the threat of the Mongol invasion due to the conservative nature of the samurai. This is especially clear because it was considered novel and radical by his peers for Tokugawa Ieyasu to use firearms and field works to hold the field against a larger enemy force. And the fact that he armed peasants with a weapon like the musket was shocking because it meant that a peasant had the ability to kill his social superior.
Community
To understand the Japanese mindset, one must understand Neo-Confucianism. That line of Chinese thought was very popular in Japan after 1600 (having been brought there by captive Korean Neo-Confucian scholars) and played a role in emphasizing the well-being of the state over the individual. However, through many and various means to create an identity of a unified nation-state, after the Meiji Restoration in 1868, the Emperor became the equivalent of the State because it was the one position that all feudal Japanese revered.
Viking communities were less dependent on a central authority and it is open to debate as to how obedient they were to their far-away kings. However, it is clear that once a king was powerful enough to subjugate his wayward feudal lords, the Viking armies were terrible to face. Which is why Pepin the Short gave Normandy to a large band of Vikings and the culture of the areas under Danelaw was a major factor in later English history (Saxon vs. Norman and what it means to be English)
Individualism
It would be an unfair thing to say that individualism was not present in Japan nor that it was as strong as anywhere else in the world. Individualism was tempered by the perceived consequences it would have on the community. A loud-mouthed son at dinner while entertaining a guest is an embarrassment to the father and elder brothers. Within the restrictions of society (which were rather broad and not terribly difficult to follow), one could do as one wished. Love was a virtue but marriages were rarely based on it.
Being Singaporean Chinese, my understanding and lived experience of it will be different from the Japanese interpretations (modern and ancient). However, the roots all come from Confucianism. Individualism is not discouraged but it is always tempered by the fact that everyone considers the consequences to others. What may benefit me may not benefit the family. I would hardly call Sun Yatsen, Chiang Kai-shek or Mao Zedong conformists. Confucianism (and Neo-Confucianism by extension) are pre-disposed towards placing one or a few at the top to safeguard the many because that was the ideal vision of the Chinese Emperor (extended to the Japanese Emperor or whichever other ruler you want to name in East Asia). If you want more classical individuals, go read the Romance of the Three Kingdoms or the Tale of Genji.
Modern cultures don't have any of the warrior of feudal stuff. But since the setting revolves around Valkyrja (a distinctly Pagan belief) and the samurai, I have limited my discourse to pre-Christian Viking and pre-Meiji Japanese histories. I could go on but I doubt anyone's read this far.
My question is, how do you reconcile the Norse sense of individualism with the Japanese submission to authority? From what I've read so far, I don't see any of the Norse influence :/ I will keep reading, of course, and if my question is already answered elsewhere, I apologize and I'm sure I will find it eventually. 
