Doumeki always ends up being the responsible one in these situations, regardless of Kunogi's doting sweetness and Watanuki's determination to be the knight in shining armor. (Watanuki is the one who feeds them and keeps them out of the rain, though tactics vary from "Would you like some more to drink, Himawari-chan? Here, let me pour that for you!" to "Hey idiot, wipe your feet before you come in or I'll be scrubbing your stupid footprints off the carpet all night.") It isn't that he minds the responsibility—though sometimes he thinks Watanuki does—so much as that sometimes it gets difficult and Doumeki has been raised to believe that practice and dedication make things easier over time, and this is one situation to which this mantra does not apply.
He thinks that Watanuki hates him a little, honestly, for being the one that carries Kunogi back from the park late at night after she falls asleep, and he thinks that Kunogi is a little melancholy when she sees them having another stupid wrestling match involving a random flailing of limbs on one part and an unruffled retaliation of self-defense on the other. He thinks that the time he found them in the midnight silence lying still on the bedroom floor and watching each others eyes with quiet intensity like strange, dark-haired owls, so close it was almost dangerous but not close enough, is the most bittersweet thing that has ever happened. He wishes Yuko-san could do something about it, and sometimes wants to hate her for being powerless in this regard but really can't because of everything else she's done for them.
(He thinks that the scars on Kunogi's back will never fade and it doesn't feel right that he can still see them printed vine-like on her skin from one eye when he's away and the two of them are home alone together.)
Domeki doesn't mind the responsibility, but he feels like a villain sometimes. He is the one who comes in late at night and makes a wall of himself between their sleeping bodies, just in case, and wakes up in the morning to find one or the other of them already gone, just because. He is the one who holds Watanuki's concerned hand back when Kunogi has scratched her face on a bramble, the one who takes the breakfast tray before she can hand it off to Watanuki the one time she tries to cook. It probably isn't fair. It doesn't seem fair. But it's the way things are.
The way things are is that Doumeki is the anchor, the barrier, the point of contact; they can taste each other on his lips and feel each others warmth on his skin and sometimes maybe that can be good enough, but not always. Sometimes at night when the guests have been cleared from the temple and the air is still but for the sounds of their breathing, and they are bundled together in very careful disarray and becoming lost in the private universe of their senses, Doumeki has to grip someone's hand tight against his shoulder because someone else's chest is just an inch above it.
They always have to be so careful, which isn't to say it's not good. It's as good as it can be, as good as they can make it, and they always try as hard they can.
But it still makes Doumeki hurt in a way he can't quite describe when he watches them press their fingertips together through the glass of the garden window, and they think they're the ones who've got it bad.