I love the postal service in Japan! :) You'll get a missed delivery slip in your mailbox or door if a postman came while you were out. If you can read Japanese, just follow the steps to get it redelivered!
Here's a summary: Call the phone number at the top of the slip (it's an automated system), and you will then input your own phone number (in case of any issues) and the ID number of the package (also written on the slip). Then you can select what day and time you want the package redelivered. Same day re-delivery is usually possible as most companies make deliveries until 9 at night. Super convenient, right? Some companies have an English option too!
Here's a summary: Call the phone number at the top of the slip (it's an automated system), and you will then input your own phone number (in case of any issues) and the ID number of the package (also written on the slip). Then you can select what day and time you want the package redelivered. Same day re-delivery is usually possible as most companies make deliveries until 9 at night. Super convenient, right? Some companies have an English option too!