score:6
Yes, you can use poste restante services in Japan, and it works for packages as well (although Japan Post helpfully warns that not all post offices are guaranteed to offer refrigeration services). Received goods are kept for 10 days and there's no notification to the receiver, although if you include a phone number they may (no guarantees) give them a ring.
Here are Japan Post's official instructions for using the service (in Japanese), and here is an informative post (again in Japanese) from a post office employee on how to do it. Their tips:
All that said, the same employee recommends using an actual address if possible. Does your friend have a friend/workplace/other that could receive packages on her behalf?