Imagine that Japan was ten times as large and located in the tropics. Then imagine fishing fleets exploring northward, into a vast inter-coastal sea, filled with various small tribes and villages. The entire stretch appeared to be like an oceanic silk road, as if the Indonesian islands stretched into the Mediterranean.
One such Japanese fishing fleet, while exploring, discovered a camping village of light-skinned tattooed people who claimed to have fled from the Celtic empire. The fishing fleet provided food, but the settlers invited the fishermen to stay with them and harvest their timber to build new boats. The village, first organized under the culture of the Japanese, quickly became its own distinct tribe after just a few generations. Being so far away from the Japanese homeland, the village became the independent city of Nara, home to the Ainu people. (the Civ Mode I used had Revolutions Enabled).
Early History
Expansion began by taking Rome to the South. The timber of Nara made for excellent battering rams, and soon the walls of Rome fell to the coastal raiders to the north. The Romans fled to Antium, but soon that city fell as well. Fishing colonies were setup across the Silken Sea - the villages of Sobetsu, Hidaka and Otaki.
Next, the Naran subcontinent was scouted and colonized. Biratori became a cultural stronghold, followed by Monbetsu, Hamamasu, Ishikari and Atsuta. To protect against the neighboring Celts, and inland Army was established. Eventually trade disputes lead to Celtic troops storming Atsuta, and open warfare befell the countryside. After nearly 200 years of conflict, the heartland of the Celtic Empire had been absorbed into the Ainu frontier. The Celts still held great swaths of territory to the West, but with their capital (and its wonders) taken from them - they were a broken people. Another war soon erupted, and the remaining cities were quickly absorbed.
The Christian faith then emerged in the heart of Rome, taught by a prophet from God. The Celts to the North soon were converted from their druidistic roots. The Ainu was a strange mix of Japanese, Roman and Celtic culture, plus the new identity of homeborn Ainu. (Plus I had a mod that let me create culturally distinct units from the parent civ in the conquered cities)
