Stein feels Spirit coming.
When he thinks back on this later, he doesn't know how to explain what happened the moment before he turns to face the oncoming weapon. It's like the sensation of someone's eyes on his skin, not something he can quantify but which he feels like something physical anyway. When he sees Spirit's face, the question of how he knew the older boy was approaching becomes entirely secondary to the fear.
Fear is a new emotion for Stein. He hasn't started feeling it until very recently, and even then it has been an emotional terror, the anticipated horror of impending loss. This is like the visceral fear that Spirit experiences during a fight but with none of the clinical distance that the Resonance grants to the meister. It is cold and it is crippling; the adrenaline in his veins locks Stein in place the way that it did when he nursed Spirit's fever in Germany, but with the addition of a raw animal terror for his own survival that overtakes his body without his permission.
It is not that Spirit is particularly physically imposing; even as he closes with Stein he lacks the height to loom over the meister, and his musculature tends towards slender rather than brawny, as Stein knows intimately. But there is something in his eyes and in the set of his jaw that Stein has never seen there before. He thought he was missing some crucial component of basic animal instinct. It turns out his instinct had just never met anything bigger than it before.
His newfound fear drags his feet backward in an attempt to run, but he only makes it a step before the desire to freeze stops him cold, and then there is nothing to do but wait for Spirit to reach him.
The weapon steps far, far too close. If this were any other time Stein would be sucking in air like he was drowning, breathing in the heat radiating off the older boy, locking the memory of Spirit's proximity into his mind for future reference, but his heart is racing and he thinks he's probably hyperventilating with terror and there is no space left in him even to appreciate the relative excess of pale skin Spirit's half-done shirt exposes.
And the red cuts across that skin. Understanding clicks in Stein's mind with a sensation he is sure must be audible just before Spirit starts talking.
"What the FUCK, Stein?"
The question is rhetorical, which is for the best because Stein is just realizing that he has never really thought through a defense for when Spirit finds out what he has been doing to the weapon. Spirit talks over any response he could make and there is nothing in Stein's head as an excuse, just the sickening horror at the knowledge that this is it, that there is no more running and no more dodging this issue, that they are going to have this argument right here, right now, and he is not ready. He is not sure that he would ever be ready for this, but this is all wrong, too soon and too fast and he is too frightened and Spirit too angry, and the weapon is yelling at him and he's not even listening, he can't even understand the words beyond the betrayed pain that laces the tone. The denotation doesn't matter anyway; the emotion of them is humming in his own mind like he is a tuning fork for Spirit's furious hurt, he doesn't need the inadequacies of language to give him a framework when the meaning is bypassing his mind and going straight into his veins.
It is overwhelming in a way that entirely redefines the word, that outstrips previous experiences so entirely that Stein can't recall why anything that came before was so frightening, seemed so intense, when now he can't breathe except in time with Spirit's half-sobbed words and his heart can't beat without the weapon's permission. When Spirit stops to suck in air, Stein tries to speak although he still doesn't know what to say. He's not certain he can handle more escalation, not sure what will happen if Spirit goes on. He thinks he might kiss his partner and he's afraid he may hurt him, and he lost control of this situation months ago but is only now realizing the breadth of his error, the extreme miscalculation when he thought this was his doing.
"Spirit," he starts, but the older boy cuts him off before he can continue.
"Don't you dare." Stein has never realized before that Spirit's eyes are always warm, that the weapon is always on the verge of forgiveness before Stein even decides on an action. It is only in the absence of that constant comfort that Stein recognizes it was there at all. "I have done everything I can to help you. I have been there for you for fucking years." Stein can't look away from the cold rage in that blue. It is horrifying and frightening and some part of him is rising to the challenge, whether to fight or capitulate he's not sure, and now there is pain under the rage too, a bottomless well of agony that Stein echoes back across with interest, and he really can't breathe at all now and is a little worried he may pass out. "I have cared when no one else did, and you've been -"
Spirit cuts off, looks away as the misery tears its way to the surface past the top layer of frustration. Stein lost control of this, of himself and the situation and his partner, an infinitely long time ago, but he can feel something rising in his blood and he knows that there is no way to stop it now but he has to try, like the desperate attempt during a fall to stumble back to center when balance is already long gone.
"I haven't -" he starts, and the denial is futile because of course he has, but he needs to explain, somehow, that he didn't mean what Spirit is taking away from this, that he didn't mean to hurt the weapon even though of course any thought makes it stunningly obvious that it would, that he has cared and burned and agonized about Spirit and that it was all a mistake, a horrible error caused by his own lost heart and fevered blood, and won't Spirit forgive him?
But Spirit steps in closer when Stein didn't think he could, and he seizes the front of Stein's coat and for a wild moment Stein thinks the weapon is going to kiss him although that seems contextually impossible. Excitement and insane hope and frantic panic are smothering Stein, he can't breathe with Spirit this close, he can't think and he can't breathe, and then Spirit hisses into his face, "Did you even care at all?"
The panic hits the rush of affirmation that surges through him, and Stein's throat closes up and he can't say what he has to say, there is too much, and the pound of absolute need crushes his frozen fear but sweeps away his ability to speak as well, and there is a tremblingly long moment of agony as Stein's head fills with feelings that his body can't express and Spirit stares at him with the cold judgment in his eyes. He needs space, he needs to tell Spirit, and the two desires smash hard into each other and suddenly he can move again.
"Don't TOUCH me." Stein shoves his hand against Spirit's chest. For a moment they are linked by his palm against the weapon's skin and the weapon's fistful of his shirt, eyes locked and both of them crying and the feedback from their mutual pain is too much, and there is no forgiveness in Spirit's eyes, not all the way down in the depths of the blue, and Stein knows then that he has lost him.
Stein's veins feel like they're on fire, like his emotions have taken raw physical form and are burning down his arm to crackle along Spirit's skin. His tongue won't work and his mouth won't move but the heat in his veins is tangible, and he shoves it down and out into Spirit, forces it into the weapon's body so there is no chance of misunderstanding. There is nothing left to save, there is nothing left to mend; there is only the destruction and the loneliness and the pain, and he pushes them out into Spirit and is not even surprised when the weapon is knocked backwards as if Stein had punched him.
Stein can feel when Spirit drops into unconsciousness, like a warm corner of his mind dropped into oblivion along with the weapon's. He doesn't feel anything but numb after that. There is a rational relief at the top layer of his thoughts, glad of the temporary protection his shock-induced distance is granting him from his own emotions, but even that is echoingly far away. There is just the loneliness, and the distance, and the spreading cold.