How do I attack NPCs outside of battle?
There is no built-in feature to allow you to attack NPCs on the map without entering battle mode. The OHRRPGCE is not really designed for that kind of game.
However, the effect can be faked with plotscripting. You can find an example at Moogle1's Plotscripting Tutorials: http://moogle1.castleparadox.com/zelda.php