Getting your arrrse handed to you is good. Otherwise it all gets a bit dreary.
Heres a quick guide to win the demo:-
Can get a costly victory on hard but have not managed any better.
The trick seems to be to re-organise your army as soon as you. move everyone onto the 'central' island.
the two katanas on your right use to block the fords on the right.
Move one katana from the centre to support the ashigaru defend the last crossing neaerst your end of the board on the left which you can cover with the three archer units. the left should be secure. The two cav units are needed in the centre.
Move one Ashigaru to intercept the Yari cav. and then surround them with your horses. You should have four (or five?) cav units two archers, one katana and two spears with another two arriving from the left. Your horse can slaughter the matchlocks and attack the katanas in rear once engaged; easy squeezy.
A horde appears in the central island form the left which you should be able to check with a spear wall and attack in the rear with your cav and archers in melee mode (they are not much use for much else without hitting your men); I supose holding the ford would be good but with matchlocks they have the missle advantage. The left should then send over some bowmen; just charge with cav.
Not long after this the white guys get hostile. You need to check them at the fords and try to position the two central archers to help. The Naginatas are a bit good and I'm never certain of this bit as there are too many of them; I find it difficult to get enough troops over there to this side. Again check them and attck in the flanks/rear. Skirmish your archers over the flat line if you want to break up their formations as they persue you.
dunno seems to work fine for me, granted nowhere near rome tw battle ai levels but on par with medieval 2. ( medieval 2 is 2.50$ on steam right now btw)
Unfortunately I never got my ass handed to me by the AI and the diplomatic screen was just annoying that no-one would bow down to my brilliance and would prefer to be annihilated than capitulate to my rule. The multiplayer cookie cutter is hugely frustrating; allways coming up against a falling line.
I'm not as bitter as I sound but after completing one campaign game I never came back for more. i must have sunk over 100hrs into it though.