Leaving and re-entering

Hi all,

This has probably been asked before but what is the specific procedure in regard to leaving and re-entering Japan for a short two week period? (Am currently on student visa)

I know we have to use the visit Japan web app but do we need 72hr pcr certificate for both departure and re-entry or just for re-entry? Considering I have not had 3rd dose of vaccine.

Any insight is appreciated