He doesn't remember how it started. But the how doesn't matter. So long as it never ends. She's holding him as if she'll die if she lets go, shaking as Yato whispers things into her spine.
The tears spattering her cheeks are not from sadness. She smiles against his neck, breathing his name just because she wants to.
Yato moves up along her body with cat-like grace, to shield her naked back from any cold. He tugs her onto her side, tight against him (Yukine has no choice but to follow), and puts an arm over both of them.
Yato takes one of his hands, Hiyori the other. He can feel his heartbeat thumping with hers, his pulse beating from his palm against Yato's mouth, and the sensations mingle and meld and he wonders for the infinite time if it has ever been any different, if the three of them have ever been disparate.
He is alive alive alive
and nothing can convince him otherwise.
#####
He used to be afraid of the dark.
The dark made him feel utterly alone, defenseless against whatever horrors lay in wait for him. Deep down he knew it was irrational, but his fear was so all-consuming there was nothing he could do.
But Yato showed him the night sky, sparkling with stars, stretching into infinity.
(One night, Hiyori brought them hot chocolate and a single blanket. Yato didn't want him to be cold, and he didn't want Yato to be cold, and the unspoken solution turned out to be him curling up in Yato's lap.
Hiyori vehemently denies taking pictures, or having any plan at all, but they know.)
And Hiyori would turn out all the lights in the house and simply hold his hand, tell him to copy her breathing, to close his eyes if that helped.
(At first they'd stand in a darkened room. That evolved to sitting on the couch. Yato would stop by sometimes and sit in a chair. One time he sat on the floor in front of them and leaned against their legs, gently. Eventually they allowed him on the couch.
When they watch movies, he likes to hold both their hands.)
Later, they would take turns holding him in bed, night lights turned off. Just to sleep, at first. But it didn't quite feel right to take turns. And then, much later, when going to bed had turned into not just sleeping, it felt even less right. So they would both hold him.
(Sometimes Hiyori wants to be in the middle, sometimes Yato, but he so likes being held and they so like to hold him that none of them feel the need to change often.)
He used to be afraid of the dark. That was before Yato showed him its beauty, before Hiyori showed him its comfort. Before those things combined into something so enchanting he didn't even realize his heart had been claimed twice over. Now…
The dark makes him feel utterly safe, invincible against anything that could harm him. He feels like the three of them have the world all to themselves, and that their love is tangible, wider than the sky and brighter than the stars.