One thing that Allen’s learned throughout these last few months is that when Kanda loves, he loves hard. It's enviable, almost. He spent nearly a decade searching and pining for the woman he (?) loved, basically devotion in human form, living each and every day for the chance to see her again. It haunted him, like the ghost of a memory was suctioned to his soul, unable to part from him - and then when he found Alma, Allen saw a sort of love in his comrade that (at the time) he wasn't aware he was even capable of. To him, Kanda was always just a stubborn asshole with a secret, biting and mercurial and prone to irritation over nothing. He believed he was bigger than he was, believed he was invulnerable and unable to die despite the fact that he was (is) still very much a human, and all humans must face death at some point. It's an order of things that defies nature, that plagues all life; NOAHs, second exorcists, the purest forms of innocence itself…everything has an ending. Everything.
Opinions have changed, obviously. From both sides, clearly. In a way that’ll change their relationship, definitely. (For the better? Maybe. Probably not. Who the fuck knows these days?) Allen can't pinpoint the exact moment things started to shift for him, but the deal was sealed the second he saw a young Kanda blearily crawling out of a vat and into a cruel world that hated him. He watched a boy, new to life, learn about the worst of humanity mere days into an existence he never would have asked for, and watched him learn how to smile despite that.
Because of Alma.
Alma.
The name alone rends breath from Allen’s lungs, brings tears to his tired eyes, hurts him a way not much else has - a pain of the heart, of the soul, bypassing every emotional wall he's ever tried to build to crash into him with all the force of ship to rocky shore. Seeing her soul (His soul? Their soul.) weeping, desperate not to be seen, not to be revealed, was one of the saddest things he’d ever seen - a person so devastated at the thought of being forgotten that they’d rather stay dead, simply to hold a piece of Kanda’s heart forever. It's love in its purest form; cruel and selfish and all-consuming. He doesn't blame Alma in the least - Allen wishes he loved someone that much.
As he is now, the only love he knows is drenched in guilt and responsibility, pain and suffering, loss and loneliness. If he could love like Alma did, like Kanda does, things might be different. Maybe he wouldn't hate himself so much.
Maybe it would be okay to let himself be loved, adored, needed. (He wants, wants, wants that.)
He watches the man in question resting, leaning against the cream wall with Mugen held close, and thinks that it may not matter what he wants. Kanda’s always been the kind of person that hates asking for permission, that prefers to act rather than faff about and wait for things to happen, and when it comes to emotions, no one can dictate what another person feels.
If Kanda doesn't already love him, he's on his way to it - those dark eyes saw in him something Allen understands but can't quite explain; he physically felt the ways in which Kanda reveres him, cherishes him, glorifies him, and it's terrifying and horrible and he hates it and he needs it (and hates that he needs it). Like an itch he won't let himself scratch, he aches and craves and can't stop obsessing over the potential in Kanda’s touch.
But Allen knows that he, like everything else, cannot defy the natural order of things. He, too, will end (and it will be soon).