There are some random factors at game start, not just the stats of each character are not the same for every new game start.
But for example, at the start, sometimes I could declare war immediately on my bordering opponent, next game I couldn't. Some things are just unclear... mechanics are very complex but one thing is sure, neutral armies shouldn't be allowed in non enemy territories. The reason is simple... army means danger to the owner of that territory and it also automatically means LOOTING.
It's like a sort of big swarm of locusts that eats whatever it can find leaving the populace poor and starving even when not really LOOTING the province and it's something INTOLERABLE for the clan leader whose territory you enter into.
I would love for this to be changed, you can't enter neutral territories under normal conditions... perhaps a military passage diplomatic opinion would do... without that, there should be an extremely serious penalty in relations when that happens without permission.
Finally, I think if you rise levies or retinues and keep them in the bordering territories, the kokujin and Daimyo of that territory should IMMEDIATELY react with a major relationship penalty.
There's only one reason why my neighbor has so many men at my border... he's preparing for war. That's another thing that should definitely change in the game.
I'm going to post about this in the main thread as request and see what people and devs think.