i am wondering if that was the entire key? that he will go off, hide and become a tree. Then again IS he a devil? What is he afraid of? not being loved? is pochita the abandonment devil? Is he a devil at all? IF devil powers did not work he would have died.
I get the feeling that chainsawman might not be a devil, and that perceived weakness he had earlier was not him losing his power, but thinking he lost it.