Soulmates!AU in which you're born with a faint soulmark, resembling the color and shape of a scar which fills with color when you're in the presence of your soulmate for the first time. And turns completely black when the soulmate dies.
LWJ's soulmark fills with blood red when the disciples arrive to CR so his soulmate must be between them. WWX's turns sky blue and he's ecstatic and then mortified that his sm would be a Lan considering their 3000rules lifestyle!
JC and NHS tease him about it but WWX doesn't really mind because he's actually really happy that he'll have a whole year to find out who his sm is. They're not the only ones whose soulmarks are sparkling with color after all, as it often happens when several new ppl from different regions convert on a single place.
In the meantime tho, one LWJ caught WWX's eye but LWJ himself is too busy trying to find his own sm to be bothered with such a shameless troublemaker boy.
But that's not the point, no. They probably find out eventually, or something. What matters here is that not only you know your soulmate is dying by the slowly or faster pace in which your mark turns black, but you can /feel/ your sm dying.
So imaging LWJ, on his knees, upper body bare, waiting for the whipping to start after the 33elders fiasco, when the first hit arrives and he falls to the floor, silently convulsing from pain at first but then not even the strong and stoic Hanguang-Jun can stop the whimpers and screams reaping from his lips at such an excruciating pain.
The elders are all bemused, because that one sole whip would have hurt, yes, but not as much as to guarant such a display of pain and horror.
LWJ can admit that the feeling of being thorn apart piece by piece is, indeed, excruciating, but nothing is more painful than watching the mark on his forearm slowly (slowly, so slowly, /too dang slowly/) turn a deep unyielding black while knowing WWX is dying somewhere in the most painful of ways and he can do absolutely nothing about it.
Now, as a mercy not-so-quite-fluff, imaging LWJ's mark turning red once again when he arrives to the Mo Village and /knows/ WWX is BACK but he still choose to run away instead to go meet him.
And now I'm thinking that maybe WWX never quiet found out who his sm was (oblivious idiot as he is) and LWJ is all like "figure it out yourself" even if he has known since before WWX left CR that first time.
Life is pain and I'm living it quiet well, thanks.