Even if he doesn't call him by name, I think the one non-Seishirou human being he knows of for sure is pretty obvious.

Yeah, his thoughts when he confirms sight of Seishin during all that are complex, but, despite being such an angry guy in general, "pissed" doesn't seem to be one of the emotions in play, does it? I assume the same thoughts you do for him there, perhaps with a healthy mix of emotional exhaustion and numbness from, well, you know, everything.