Kurama is not oblivious to the reality that Hiei doesn't look any better. Despite this, he's reporting some improvement, and that's what the fox is focused on. Both in a good faith effort to trust that he knows his own body, and because any change in the right direction is something. Minor as it may be, one day at a time as far as he's concerned.

Still, he's watching him carefully while he drinks that water, eyebrow raising at the fire apparition's response. His head tilts curiously when he laughs with those words, bypassing the first thing Hiei says to answer the latter with a bit of caution to his tone.

“Why wouldn't I be? You're up, moving around enough to visit the garden, and your appetite seems to be returning. All signs of improvement.” He would know, he's seen enough illness in his life. “You do want to get better, don't you?”