Most people don't understand why Shinkai likes Arakita so much. They look at Arakita and see what he is, and they look at Shinkai and see what he isn't, and he can see the confusion in the back of their eyes even if they don't say anything.
It makes Arakita hiss, and it makes Shinkai smile, and all they ever see is the pleasure in the expression. They don't see the shadow behind his eyes, the teeth behind his lips, the darkness in his thoughts. He likes it that way, it's better this way. For a long time that's all he tried to see too. He'd stare into the mirror and wait until the blue in his eyes turned shallow and opaque, waited until the wall came up, high and strong enough that he couldn't even remember what was on the other side.
Arakita's teeth are always bared. Shinkai loves that about him, loves how naked his aggression is, how he'll all but snap his teeth at anyone who looks at either of them too long. He loves that if someone has the nerve to say something Arakita will lunge forward like he's going to tear their throat out while Shinkai smiles and holds him back. He especially loves after, when he can drag Arakita to a moment of privacy so the other boy can turn those teeth onto Shinkai's skin, bite blood into his shoulder and scrape possession over his back, under his shirt where it's half-covered.
"They don't even know you," Arakita says, like it's a personal affront. "They don't see any of you."
"I know," Shinkai agrees. The pain is satisfying, runs hot through his veins until he can let the tension of his facade melt away, because there's only Arakita here, after all. "You do, Yasutomo."
"Shut up." Arakita crushes Shinkai's words away under his mouth, bites down on the redhead's lower lip until the metallic taste of blood spills over Shinkai's tongue and Arakita pulls away with his lips stained as dark as the other's hair. "You should show people, let them see you're worse than I ever could be."
Shinkai blinks at Arakita, can feel the wall crumbling like sand as his eyes turn dark, as he smiles, as he tastes the blood staining his teeth vicious red. "You know." Arakita's gaze drops to Shinkai's mouth, his focus sliding away until even his perpetual scowl slips into something more like heat. When Shinkai reaches for his shoulder Arakita lets him, lets him shove the other boy up against the wall and step in to reverse their positions. Arakita's shaking under his hold, trembling with the adrenaline of want, and Shinkai can feel his own restraint giving way, melting into the uncontrolled strength he usually keeps tied down.
"You know," he says again, leaning in close so he can lick his blood off Arakita's mouth. "You know what I am." Arakita hisses, opens his mouth and Shinkai takes the invitation, presses his tongue against the sharp edge of Arakita's teeth and feels out the radiant heat of the other boy's mouth. "And you like it."
"What's not to like?" Arakita says with his usual vicious hiss, though it's undermined by the hands dragging Shinkai in closer. "This is what I want, not the bullshit you usually offer to the world." His fingernails catch against Shinkai's back again, dig bruises in against the redhead's spine while Shinkai closes his hands on Arakita's hips and presses as hard as he can, lets all his strength flood into his fingers as he squeezes against the other.
"Ow," Arakita protests. "Fuck, this exactly." He arches up off the wall, leans back on his shoulders so he can rock his hips forward and into Shinkai's. "Be like this."
"No," Shinkai says, and leans in to bump his head in against the other's shoulder. "Only for you, Yasutomo."
"Fuck," Arakita growls. This time his teeth catch Shinkai's neck, above his collar where he won't be able to hide the mark. Shinkai shuts his eyes, doesn't stop him, just leans in to push himself in against the other's body so Arakita can feel his reaction.
It's a relief, sometimes, to let his guard down.