He has done everything in his power to avoid it. He has fought and ranted, run away and brooded, gathered his courage and fallen apart. His struggles have landed him nowhere but in the thick of it, and it wears on him every day. He doesn't know how long he can hold out.
He doesn't know how long he can drive in the same jeep, eat at the same table, drink from the same canteen, sleep in the same room as the boy without grabbing him and kissing him within an inch of both their lives, lives which could be ended at any moment by a lucky assassin or a determined god. Sometimes he thinks that it's hopeless and if they're all doomed anyway, why not give in? But to admit would cost much more than it does just to know, and oh how it aches just to know.
Sanzo knows he is in love because nothing else hurts like this.
Like his heart is constantly in his throat, like his bones are made of hot iron, like there is a gaping wound oozing through his robes. He feels naked every time their eyes meet, and his breath catches a little when he spots Goku in midfight, an enemy's blade glinting as it flashes downward. All he can think of for that split second is the sound - a solid, thick noise of a sword piercing a ribcage - and the blood - everywhere, staining white robes - and the paralyzing fear and loss - kneeling, weeping, when they found him. But then the weapon is deflected and Sanzo pulls the trigger - ~can~ pull the trigger after that moment is broken - and the enemy falls.
He knows he is weak. He knows the boy can take care of himself. He knows that his own preoccupation could endanger them both. A battleground is no place for weakness, when even that split second of hesitation could mean death.
Sanzo is terrified of losing him.
Fear makes him angry, and so he takes out his frustrations on the boy - the object of his desires, those unholy thoughts and wishes that come to him at odd times. He reads his morning paper and Goku eats breakfast, but then he turns his head a certain angle and catches early sun in his eyes and they seem to glow. They seem wild, the amber eyes of beast, and a shiver traces Sanzo's spine because he wants to reach out and... Instead he bunches his paper and thwacks the boy across the back of the head and calls him an annoying stupid monkey with the table manners of an ill-bred goat.
Or something along those lines. It doesn't really matter these days. Because Sanzo is starting to think the boy knows.
A veiled look will cross those guileless features sometimes when by chance Goku has caught him looking in the rear-view mirror at him. Or he will take something too far as if solely to get Sanzo's attention, even if the attention is a swift cuff or a sharp word. Or he will follow Sanzo when Sanzo would rather be left alone because another presence is too much for him to bear, and yet Sanzo will let him stay and he knows Sanzo will let him stay because that is Sanzo's weakness.
All Sanzo wants is for someone to stay.
He knows he is a cold, conceited bastard. He tries very hard to make himself this way, though it isn't all ~that~ hard. He has always been aloof, and he knows exactly his strengths and weaknesses. It isn't conceit if all his enemies really ~are~ no match for him. And they aren't. It really isn't coldness if he really doesn't care much for anything. And he doesn't. Or at least, he didn't.
But then he had to find this wretched child in a cave and was damn fool enough to take him with. He's had no peace since, the constant whining, babbling, laughing. Crying sometimes, too. The messes and stray animals in his office at the monastery - he still has an inky pawprint on the corner of his desk. And his ire for these offenses has been great. Sometimes he says horrible things, things that bring a tell-tale glimmer to Goku's odd eyes, things that make them both stomp off to cool down before they do something worse than throw words at each other.
But Goku hasn't left yet. It's been years and Goku is still at his side constantly, usually smiling in that oh-so-irritating way that makes his lips curve in a perfect, full cupid's-bow, sometimes glistening because he's just licked his lips as he's talking, with his hair mussed just ~so~ by the thick gold diadem and the wind from the long ride in the back of the jeep. Goku takes all the verbal and physical blows Sanzo can dish out - and he knows he is irredeemable for it - but never once has wavered in his faith in Sanzo. It confuses Sanzo, this intense loyalty, this almost-adoration. No one should trust him, no one should stand by him, not when he is cruel and remote, not when he tries his damnedest to push them away. Yet Goku does, true and fierce and innocent with his simple thoughts and ageless youthful body.
Sanzo knows that if one day Goku should leave, should fall away, should die, there would be no future. Sanzo can't see himself going back to the monastery and pushing papers for the rest of his life, can't see himself defeating Kougaiji, or even going to breakfast the next morning if Goku isn't there waiting for him with that smile and that laugh and all the aggravation and irritation he brings with him. Sanzo knows he will not live longer than Goku because he doubts he could keep his finger from pulling the trigger one last time. Because that is the other weakness, part of this double-edged sword that somehow became lodged in his heart, the blade he can't remove because he would bleed to death if he tried.
All Sanzo needs is someone to stay for.