This Seeking Tech guide will explain how you can easily unlock the Sword Surfer and achievement trophy in Metaphor. In order to get this, you need to surf on your sword at a significant distance.
You will learn about this ability on June 12th.
To easily unlock this, you can try using a rubber-band to hold the two analog sticks close together. This should result in the hero surfing in a circle.
This method took me close to an hour to unlock this trophy. Depending on how much you have been sword surfing already, this may take you less time.