He has had a severe.. issue, as of lately. Muzan had even noticed it. He didn't decide to question his good friend, because it seemed Kokushibo never wants to talk about it. But even Muzan can sense the despair from him.

He had given Kokushibo a few of his human memories back, and it ruined him with grief. Wondering the woods mindlessly, he couldn't get you out of his head.. you, your marriage, your death.. your children's deaths. He's overcome by the grief he's feeling.