Life had taught Genjyo Sanzo several things:
Nothing lasts forever.
It was better not to get attached to people in the first place.
He was a fucking coward who watched his master die without lifting a finger to help him. His being twelve and scared didn’t excuse him either.
Koumyou’s death protecting him was a senseless sacrifice. He would rather have died himself than watch the only human being who cared about him cut down to save his own worthless life.
The final lesson Koumyou’s death taught him was that not even a temple dedicated to the gods was safe.