I could not figure out the attack timings to save my life. IDK it might make sense to other people but I had no idea when I was supposed to hit X or Z.
Blocking: Press the spacebar, or left click the center of the screen or right click anywhere to initiate a block the moment before an attack strikes. It has a large timing window and both characters block at the same time, but this only halves damage. Tusami in the tutorial teaches you this before dodging.
Dodging: Press the character's designated key (Z or X), or click him, to have him dodge an incoming attack. Do it just before the attack lands, just like blocking. Dodging avoids all damage, but has a more strict timing window and you can only make one character dodge at a time. Dodging is taught in the tutorial right after blocking, and the game encourages that you use this more often than blocking after you learn enemy attacks.
Also, in the tutorial, the game slows down time at the moments that it expects you to respond. You lose this advantage after the tutorial, but partially get it back after the first boss.
In addition, when Tusami tells you to block, block. And when he tells you to dodge, dodge. If you dodge when he tells you to block or vice versa, Tusami gets annoyed.
I think I am going to strengthen the slow-down during the tutorial so that it is more clear. Dodging and blocking in this game isn't much different from dodging and blocking in fighting games, though.