No, I dont mean the eventual hostilities, or Daimyo honor. I know everyone will attack you at the end. But I am suspicious of that the oldest and strongest allies backstabs you, no matter whatever you do to please them.
Once, I started a campaign with Tosa. As you know, you start on an island isolated from mainland, with 3 other neighbours. I smashed the first enemy on top in few turns, and had very good relationships and an alliance with the one on the right. Then suddenly, the one at the top right declared war to me. I thought "It is ok, the game tests you... It supports Shogunate, and its fun to have an enemy anyway." And then, next turn few more clans from long distance, had joined the war against me. (By the way not even the most friendly clan accepts your alliance invite if you have no borders. But everyone feels free to declare war no matter how far they are. So frustrating) I destroyed the second clan on the island, and since I was very friendly with the third, I was thinking to step to the main island.
Then wham! My neighbour changed his side for the Shogunate, and changed from fery friendly to hostile in 1 turn. Next turn, he declared war on me.
This kind of stories happens on my "every" campaign. Somehow, in few turns everyone left me alone.
I know the diplomatical balance is very fragile in S2TW, am I missing something? Maybe che character of the clan? Or Daimyo honor? Can you say "No, you are dreaming, you are just an old wolf who plays S2TW like STW, and complaining about diplomacy"?