Whats the shortest Japan trip you would be willing to take?

For me, nothing less than 14 days because 2 of those days would be eaten up by the flights in/out

*follow up edit* I have only been once, 16 days in Feb 2024. If I magically found JAL or ANA special fare ticket like 600 or 800 round trip I would definitely consider making a 5/6/7 day trip. So right now I am planning to go back beginning of April for another 16 days, one week in Japan (Hiroshima/fukouka) one week in Korea – baseball, baby!