Responses
We won't know for sure until next chapter but I think his statement is a form of questioning. That and the fact that Hee-ryang seemingly shows Moon-Won the room where he kept Yeonjo, I really don't think this is about grief at all. But we'll see.
Actually,you are right. Hee Ryang meticulous streak wouldn't be parried by grief. I think he will get to the deepest of this situation until he can 100% prove tha Yeonjo really did kill himself.
After all, he knows Yeonjo is incapable of killing his own and Hee Ryangs.
His face and what he said in the last panel do not coincide at all.
His face is not showing any signs of grief, more like a man determined to know what actually happend but in a pissed off manner. (His face card though, ugh never disappoints!)
But, what his statement can also be intrepeted that he wanted someone to also grief Yoenjo's passing?
I think I wrong though.