Yamanato

It is a world still untamed, still existing on the boundary between the highest and lowest values of the Imperial Cult and the needs and goals of the Imperium of Man and in utter reverence but total nonunderstanding of the Adeptus Mechanicus. The people there are refined and loyal to the Imperium, yet shockingly brutal to their own and barbaric in the pursuit of war for dominance over the planets agricultural and aquaculture incomes.

History
Yamanato was colonized in the Dark Age of Technology by an ancient Terran, allegedly East Asian nation composed of a mix of the populations of a separate island and peninsular nation whose names are remembered as Koryonga and Nigon by the various clans of Yamanato who trace their lineage back to the ancient nations, with approximately 74% of the populace hailing from the Nigonjin ethnic group.

Existing in a state of technological advancement, silica animus began to control most of the functions of the world until the uprising of the Men of Iron spread through the settled human worlds and led to the beginning of a costly war.

They were almost destroyed putting down a Man of Iron uprising and flooded most of the planet in the process

It was easily recaptured by the Ordinators in their first few years in the sub-sector

and many serfs were taken from the greatest clans that joined the Imperial cause

Culture
The people of Yamanato maintain a primitive perception of the Emperor's divinity which is constantly being corrected by preachers of the Ecclesiarchy to turn the world to the Imperial Cult proper, though only 9% of the population claim adherence to it. 91% of the surveyed population adhere to a religion known as Amakameka, throughout which the believer population was converted to see the Emperor as their once "hidden" sun god, Amabutsu. Many other far lesser gods are believed to exist, most of which can be clearly traced to have their personas assigned to the actual personages of primarches or great Imperial saints through the subtle manipulation of clever fringe Ecclesiarchial missionaries.

Given their entrenched belief in a system of clans run by feudal warlords and the fact that modernizing them all was predicted to lead to frequent, bloody wars, they were left with minimal technological gifts

The greatest warlords, called the Daimbaega, including the planetary governor - the Shogajibaega - have elite forces of lifelong samurai-like troops called Bushisa who fight with las-locks and rare disruptor-field power katanas (edited)

the Ashisa are their ground troops who fight with literal matchlock guns, and unaugmented spears, swords, and halberds (edited)

they measure wealth in rice and seafood production that they use to meet their tithe. Ferunus gifted them equipment to conduct sustainable mass fishing and tiered rice farming operations overseen by Magi Biologis assigned to each clan like a Maester in GoT. But unlike a Maester, they are seen as the chosen of the god of agriculture, technology, and nation-building - Lord Okuni noui Gorugona (now conflated with Ferrus Manus).