Still wondering what kind of man Tsubaki will fell for in the end.
Strong one, friendly, smart, fatherly figure, hot guy with dark presence or typical clumsy but cute?
What came to my mind a while after reading this chapter: Did the guy just transform into a tanuki after hearing girls playing around in the onsen so he could spy on them? He should have been able to hear them roughing around even if he wasn't a ninja after all.
@bloquer That's one take. But when considering it I think it was mostly to let them know it was time to go.
Since he's undetectable, he gotta make some kind of signal. And it has to be a signal that doesn't encourage the youngsters to go exploring. (Plus if it is some kind of "ninja magic" then it might not be possible or reasonable to "turn it off".)
So lazy solution is to just waltz in as a tanuki, let sensei see him and then walk away to wait elsewhere until they're done.
(Or possibly he might have thought it was the ruckus of some young ninja boys. High-pitched voices and childish excitement can be pretty similar in sound.)
I agree that it is rather unlikely that he wanted to spy on them, it is just interesting that he did it that way instead of say listening a bit in from the distance to hear if he recognizes for example the voice of the teacher and then make some owl noises or something to give her a signal. They seem to know each other quite well after all.