Goku is still standing in front of the mixed dirt and snow that marks a grave. Sanzo doesn't know what he's thinking. It could be many things; thinking about how he held Gojyo and Hakkai back, perhaps, or about his limiter and the Minus Wave and the murmur of Seiten Taisei in the back of his mind. Perhaps he is thinking about friendship and children and madness. Sanzo is ready to leave. He had heard the Minus Wave whispering here long before the madness struck. He doesn't get attached enough to need to say goodbye.
"Hey, Sanzo... If I..."
Ah. Thinking of his limiter, then, and how it feels to take it off. Wondering if that madness is like the Minus Wave. Thinking of being put down like a rabid dog. Sanzo is tempted to smack him upside the head and knock some sense into him, but just a glance at the plane of his shoulders shows Goku's doubt. It'll gnaw away at him if it's not addressed here and now. Sanzo lights a cigarette.
"Ah, never mind, it's nothing." Goku pastes a smile on, an expression that comes easily to him, however false it may be. Sanzo sighs, watching the steam/smoke of his breath dissipate into the crisp air. Very serious, then - too serious for Goku to want to face head-on, as he does most things. Too serious for Gojyo or Hakkai to step in, for they are just watching. He doesn't make them wait.
"I would kill you," he tells Goku, and even as he says it he knows it is true. He cannot imagine Goku would ever even hear the silent thrum of the Minus Wave, but if he were to be a rabid dog, he would need to be put down. He says it again, quieter but fiercer, just to see that startled expression and lingering false-happiness on Goku's face disappear. "I would kill you."
Goku is quiet again, not even his feet whispering against the snow. Sanzo sees the doubt leave, sees the comfort that is inherent in not needing to struggle.
"Alright," Goku murmurs, and it is enough.