Aragami: Shadow Edition

The skill is unlocked via Aragami Skills tree menu (1st one)

its in the 1st line of skills and the 2nd option requiring 3 skill points (scrolls)

the first one Shadow Leap cost me 1 point (required to progress & this achievement)
the 2nd one Ledge Kill cost me 2 points (required for this)

Then simply Perform a Shadow Leap () next to a guard on a ledge above you (i.e.; a climb) that will result in an instant kill & achievement.

Youtube video courtesy of ted x RAD0 x
(video solution is @ 40 seconds in.)