Knights and Bikes

This can be done right after acquiring the throwing disc from the mini golf course on Day 2.

Easiest way to do this is with 2 controllers. Right after you get the disc, you'll be outside on a long vertical trail leading to the course. I positioned Nessa at the bottom of this trail and faced north. I positioned the other character slightly above her, facing north as well. You have to throw the disc with Nessa ( on one controller), then kick it further north with Demelza ( on the other controller). The disc will travel further north, hang in the air for a bit, then snap back towards Nessa. You'll need to kick it again with Demelza, and loop this 5 times. The timing is a bit strict, but it's easy once you know how close the disc needs to be to your character. Kick the disc 5 times and the achievement unlocks immediately.

Once my video is uploaded, I'll link it in this solution to provide better clarity of the spacing/timing I used (EDIT: below). The achievement didn't pop in the vid because this was the second time I did it to record.