Manga: Ao no Exorcist

[Munsu]

sensitive? yes.
but not essential. other than a small lose of balance (for a short term of time at first, and in the long run, only for high speeds), the loss of the tail doesn't really bother mammals.

so, Rin should cut have his tail cut? where did I see this before?

I think Mephisto said something about hiding it.