How to beat Shadee the tutorial boss:
Beating the tutorial boss is actually quite easy if you follow the following rules:
1) Defend at all times.
Remember that even if the R shoulder is held that after a cut-scene you won't be defending. You'll need to release and repress R fast to avoid damage.
2) Don't bother moving around unless you want a better camera view - it doesn't really help the fight.
3) Watch the boss fight.
Her worst manoeuvre is those double swords upwards. If you're not defending (i.e. counter-attacking) when she does them you'll toast up to 30% of your life. Therefore the objective is to avoid them. The ONLY way to avoid them is to counter an attack just after them. It's too hard to predict when she'll do one, just that she won't do two immediately in a row.
Wait and bate her by moving if necessary into doing a sequence (remember you're ALWAYS defending). When the swords thrust up, wait until they've pulled down for her down hit and bang [square] (all the time defending) to counter-attack this particular attack.
You'll always do a clean counter hit and only on occasion take damage. Be patient, ensure you started with maximum health and you'll always win.
Sadly when she's down to 25% you wuss out, loose focus and get slaughtered, but this is a narrative slaughter rather than the humiliation of having to restart the tutorial.