Well, i had a similar need, wanted to make a bullet, which, when hits the body(enters its area), it subtracts HP and queue_free it self
i did that by first referencing script
var danger = preload("res://bullet_scene.gd")
(which is a script for bullets and slashes and such..)
then you add a Area2D script to first object, add a 2D collision shape IN that Area2D same for 2nd object
and add signal to the script, like ...
func_on_www_area_enter( area ):
I found that for bullets at least, you shouldnt use kinematicbody nor physics one(with separate collision node as well), cuz then it wont work well with detection when speed get high