If we handle a National Phase Entry (or a domestic Japanese application), a Power of Attorney (POA) is not necessary (this also applies to all subsequent prosecution stages). However, if we take over your case from another agent, a POA is required, but your signature is not, so there is no need to mail a physical copy. Please note that for critical procedures, such as patent reassignments, a paper document executed by the owner is necessary, and in such cases, you will need to physically mail the paper.