Sasori loves poison.
He mixes it himself for all his little experiments and half-finished puppets, or whatever his need might be. The doses vary from crippling to deadly, if used correctly—enough to fuck a person over, physically or mentally. It's beautiful, the way everything ends in a second, and all from the smallest shot of liquid, freezing life forever.
And sometimes he even injects it into himself, sinking the needle deep into his wrist and laying back in the afterglow of a drug as numb as his senses. Slowly it seeps out of his plastic skin and snakes it way down his outstretched arm, wrapping around his fingers like ivy; leaking from him like a disease. A disease that will never kill him, a disease that can only fascinate him because it's so far out of reach.
Sasori sacrifices himself countless times to the black waters, never quite feeling the burn he needs.
He never misses his own flesh though, no matter how dull reality can feel sometimes, for now he has everything he ever wanted. He is art, he is eternity, he is beauty; just a shell with a soul roughly carved into lost innocence. Complete and whole and immortal, everything he ever can or will be.
Sasori loves poison, but Deidara does not react as well to it.
A mild needle with less than a drop pierces the boy's skin; and he's loud at first, screaming and seething through gritted teeth as the first flood hits him. In time he learns to hush, merely laying quietly—but never silently—in his danna's protective arms. He gives in to this mind-fuck. Sasori holds Deidara as he twitches, running his fingers through his hair.
The poison calms them both.
He leans down to kiss Deidara, and his lips taste like ash as his breath echoes poison. It's only countered by the sickly sweat that drips down Deidara's face to rest on his lips, and combined the taste is more deadly than arsenic, more addictive than heroin. Cold, contaminating and always burning through their veins.
A twisted practice, but one which Deidara knows will come to an end—everything must, after all, as nothing is eternal. Not even this art. And he knows that the drug will never truly kill him, no matter how many times he falls at the altar; the puppet master does not toy with the walking dead.
Sasori loves poison, but it doesn't mean anything to him on its own. With Deidara he can feel that he's still human, under the mess of necromantic heartbeats and cheaply packaged morality.
I love you, he murmurs, and the words course violently through Deidara, stronger than any poison Sasori could desecrate him with. And Sasori wants to believe his own words, but like the poison, he's come to realise that he'll never truly feel Deidara.