"Fuck," Leo moans in Japanese, hands shaking as they slap against the glass. Dirty, his mind whispers, the glass is dirty, and even if that doesn't mean much to a mutant freak like him it's still so very dirty. Perfectly, beautifully dirty. 
Dirty like the rooftops he can still glimpse through, where anyone could squint through the city lights and see. Dirty like his own reflection in the mirror, with his cock throbbing helplessly between his legs as his eyes roll and his cheeks flush, dirty like the porn-star moans he can't keep from echoing around the abandoned office. 
"I meant what I said, Leonardo," Usagi purrs in his ear, and his voice is dirty, too, almost as dirty as the cock he's pushing into Leo's aching hole. "It really is an--ah-- lovely city. A good fit for someone as, mmh, pretty as you." 
Flirt, Leo wants to say, but it comes out a quivering whimper instead. Usagi chuckles gently in his ear and grabs Leo by the hips, squeezing hard enough to bruise as he pushes himself that much further in.  
A desperate squeak escapes him as Leo writhes like a pinned butterfly, struggling to get in a full breath. Drool fills his mouth, and he shamelessly lets it drip down his chest, glistening with a silver-wire sheen. 
"I think," Usagi murmurs, like velvet in his earslit, "We....nnh, ought to put a picture of you up on some of those...billboards, you called them? Put a bit of spice into all those busy little lives. You'd leave them breathless, Leonardo, dancing... huh, on my cock like this, stuffed full and desperate. They'd never want to look away." 
There's a rational little voice at the back of Leo's mind whispering about how ridiculous that is, how they'd be more likely to scream in terror and run for their lives, but Usagi gives another slow roll of his hips and the thought splinters into more incoherent squeaks. 
Leo props his sweaty forehead against the glass and the lights seem to blur before until they really look like a forest of eyes gazing hungrily up at him, like the distant roars of engines are people calling his name. The thought is enough to make his cock dribble a little, and he feels so good he can't be ashamed of his own arrogance. 
"Perhaps," Usagi gives Leo's cock a thoughtful squeeze, then quickly lets go as he gurgles helplessly, "We should add a little bit of color to the picture, first." His hand comes down with a brutal slap, and it takes everything in Leo not to come from that alone. "A bit of rosy pink." 
He keeps hitting Leo, again and again, in time with his slow, steady thrusts. It hurts, but in the best way, and it doesn't even occur to Leo to fight back. 
"Good boy, holding so still for me." The words sound a bit like what heaven might taste like. "Such a sweet little thing." Leo lets out another greedy squeak at the words and Usagi laughs. "Oh, you like that, don't you?" 
He does, he likes all of this so much, likes the pain and the praise and the idea of being full for the first time in a life that has so often felt painfully hollow. Usagi could fuck him in the ass in the middle of Times Square and Leo wouldn't whimper, as long as he got to feel like this for a little while longer. 
"Of course you do." Usagi gently tugs his head back a little, enough for Leo to get a better look at his own panting, whimpering body. He can see his own cock shaking and dripping, on the verge of the night's first orgasm. "Look at yourself, Leonardo, look at how perfect you are." 
From this angle Leo's body looks almost like it's superimposed over the city through a holographic projection or some shit, like everyone can see him, want him, without a chance in hell of having him. Because he's Usagi's now, safe and warm in his arms, and nothing will ever hurt either of them again. 
"Fucking hell," Usagi gasps, the curse so strange and perfect as he grabs Leo by the mask and turns his head, pressing their mouths together. "I love you," he whispers; Leo swallows the words whole, buries it in his stomach where it'll grow into something beautiful. 
The city watches them, loves them as they love each other. It holds them close as a mother when they break apart, their light spilling like stars that break to form anew.