After Aya gets attacked whilst sleeping, Her and Reiko run out of the shack. Aya is not wearing her cowboy hat but in the next shot outside the shack she has the hat on
When she places the sword on her sister's grave, Aya still has the bloody cut on her face that she received during the final sword battle. A few seconds later, the cut is gone and remains gone for the rest of the scene.
Reiko fires her double-barreled two-shot shotgun repeatedly (several dozen times in a rapid succession) without reloading. There's also no recoil. This is due to Reiko in the Onechanbara game series having a shotgun which does not have to be reloaded.