He enjoyed sleeping under trees during his travels outdoors. This was problematic. More than one Mushishi whom traveled with him at one time or another warned him about this.
"Watch out for Kagedama."
"You'll catch a Kagedama if you're not careful."
He understood this.
But, even if he were to get a Kagedama, what would he possibly forget? The Mushishi who could be of help in the future? – He could find others. The Mushi and the way to rid of them/ stop their effects? – He could learn them again easily. And he still had his Mushi scroll with him. Forget his name? – He would be fine with making up a new one, oddly.
It wasn't something that he very much worried about. (That still didn't mean he was okay with it, though.)
So, he always checked the shadows under the trees, expecting to see a long tendril of darker-than-usual shadow to stick out.