I started conquering Otomo during turn 50+something and finished at during turn 78.
Conquering was not difficult but ruling is, extremely.
The first province I captured from them was Nagato.
After more than 10 turns, there is still no sign of improvement in the happiness of the population there. As a result, I had to exempt it from and earned nothing from them.
Similar problem occurs to the other provinces.
The main reason seems to be Christianity (my clan's religion is Buddhism of course).
To make the matter worse, I had to maintain sizable armies in those provinces besides exempting them from tax.
All in all, I was losing a lot of money from those Otomo provinces.
What did I do wrong e.g. attacking them too late?
Best Answer
If the provinces are primarily Christian while you are Buddhist, the province will experience significant unhappiness caused by religious unrest. To avoid this, you'll need to convert the population to Buddhism. Do this by:
Converting provinces takes time, especially for former Otomo provinces since their faction buildings provide major bonuses to the spread of Christianity. While the province converts, you'll need to use other methods keep the population in check:
If the provinces are expensive and hard to hold, consider taking them slowly and giving them time to convert before moving further into enemy territory. Keeping extra armies nearby can be useful to help with rebellions and any enemy counter attacks - provided you can afford them. If you can't, consider balancing your budget by demolishing the more expensive buildings in the new provinces that do not contribute to conversion, happiness or repression. Once the provinces are largely converted, you can start taxing them and rebuilding the lost buildings while your armies move on to other enemy provinces.