The majority of sound design in the electronic genres are simply applying ADSR envelopes to the volume and the filter cut-off of a synth.
This sound (and all other nice electro plucks) are ALL about the ADSR envelope controlling the filter cutoff of a low pass filter.
Any pluck starts with this starting point, and then just gets tweaked from there.
- First put the low pass cut off at midway starting point.
- then put the routing/control of the ADSR env generator the influence the low pas filter about +50%. This control is usually at mid point/neutral. So midpoint = 0%
- then put said ADSR envelope attack=0% decay=25% sustain=0% release=0%
Once those are set from there, the three parameters you want to tweak to modify the sound are Low Pass cuttoff , ADSR decay time, and env to filter control.
What about the oscilator that we are filtering? Well for this particular synth, it is either a square wave or more likely a series of sin waves at octaves - which is essentially a a square wave with less overtones.
This is with 100% certainty the method used for this kygo pluck. Just tweak those 3 parameters and play with the oscilator type.