I don't own Young Justice.
He's always there, even when Roy tells him to leave, tells him he shouldn't watch this, shouldn't be a part of it, should just go away and never come back because you deserve better than this. He's there because he knows Roy only says those things so he can clean his hands of the guilt of this, because he can say told you you should've gotten out of here while you could afterwards and pretend he gave him a choice, when really there wasn't one, isn't one, will never be one. Kaldur could never leave him to do this alone. It's a fucked up habit – not as fucked up as Roy's, of course – but he's there to watch him every time, to stand behind and hold Roy's shoulders as he slides the needle deep, to press his lips to Roy's neck and feel his pulse flutter and falter and slow as the drug takes hold, to whisper reassurance into Roy's ear until he finally stops telling him to leave.
And when the rush comes, and Roy pushes him against the wall with eyes sharp and hazy all at once, Kaldur will find himself trembling just the same, ecstasy boiling in his veins as Roy's hips shove his back into the wall and Roy's fingers tear his shirt away from his chest and Roy's mouth crushes his own in something that looks like a kiss but is really a just a mindless, desperate claim. Pretty soon he can forget the dryness of Roy's lips and the violence of his grip and the vacancy in his expression. Pretty soon he can lose himself in the way Roy is losing himself, and surrender himself to mindless pleasure until the next crash, when he can wait for the next high.
Roy only touches him like this when he's shooting up. Kaldur tells himself that this isn't why he doesn't stop him.
And it isn't, not entirely. He's watched Roy not do this before, and it's worse, so much worse. He's been there all the nights Roy has woken screaming, drenched in sweat, has held him as he's thrashed and cursed and even cried himself back to sleep, begging Kaldur to make it stop, angrily whispering all the reasons Kaldur shouldn't even be there. He's been there all the days Roy has just sat there and stared at the wall like nothing mattered, has reached out to catch Roy's hand when it strayed too close to the drawer where he keeps his only handgun. He is there every time, because no one else will be. The others gave up long ago.
Some part of him is ashamed when he's like this, gasping helplessly as Roy curses him between thrusts, when he's returning every bit of Roy's hissed hatred with an unspoken, unexplainable, uncontrollable love. He knows he isn't the only one hearing it all, knows there are people looking out for him who still keep watch for his sake, and it makes him burn somewhere deep inside that they will know this weak, ugly side of him that only Roy is supposed to see. But then he thinks of how they all abandoned Roy to himself, watched him spiral towards inevitable self-destruction and did nothing to stop it, even the people who were supposed to be his protectors, and then he thinks let them hear it all and drinks up every spiteful word that drips from the archer's mouth.
"You made me this way," Roy will growl, voice raw with anger and sadness and utter senselessness as he shoves Kaldur into the mattress. "You could have stopped me and you didn't. You made me this way."
Then in a few hours, when they are lying still in bed facing opposite walls, Roy will roll over suddenly and pull him close and whisper a thousand apologies and kiss all the places he struck (all the ones he can remember, at least), and beg him never to go, and the loneliness in his voice will kill Kaldur even as it saves him, even as it gives him a reason to stay, even as it fills that gaping hole in his heart where he needs to be needed.
It's a fucked up habit, but every time he tells himself it has to end, he thinks of all the passion and the anger and the lust and the increasingly rare moments of tenderness in between it all, and tells himself just once more.
Sometimes he has to wonder which is worse – Roy's addiction to the drug, or his addiction to Roy's.