Not really an arc, but it's some sort of guide.
First of all, the character who will die (I'll call him DC for dying character) must have some intimacy (doesnt have to be romantically; it can be sibling bond) with your MC. The readers doesnt necessarily have to connect with DC, but they MUST know that DC will affect MC if he were to die.
How about after the death of DC? NEVER skip on the MC's emotions; let their grief, sorrow, and rage flow freely and it must be felt by the readers (even though the readers themselves may not care for DC, they at least know that the MC does, so the death of DC still impacted them through the MC).
DONT DO A TIMESKIP without letting the MC's emotion flow completely. Why? Well, imagine that you threw a ball high up in the air, and you look away for a few seconds, then looking back, you see the ball resting on the ground. How dat happened, right? Well, obviously it reached its maximum height and went down, but we don't know how high up it goes and how it falls down; all we see is that the ball is going up and it's suddenly on the ground. It destroys the immersion. The readers want to see how high up the ball goes (in this case, the emotions of the MC) and when it starts to go down (the MC is healing); and when it starts to descend, you can now either do a timeskip or show how the MC is healing.
For the (character?) arc itself, I have no idea who you want to create an arc for. For the MC, after the death of DC, you could simply show how his death has affected him whether it's done emotionally or mentally, and how he heals and move on. For DC, like I said, you don't need your readers to know the ins and outs of him, it's already enough that the MC cares about DC; and I don't recommend creating an arc for a character whose role will end up with him dying, as it's a waste really, but if you still want to, you shouldn't still create an arc but instead create a DC that readers can empathize with; this can be done by giving them a tragic backstory or goal.