The bank letter certifying the amount being approved is embassy specific. I submitted such a letter in Taipei and was told they would not accept it even though the website stated it was acceptable. Was told 'we want to see transactions for the 500K" Had to rush to get bank statements printed out.
Ok..In Japan foreign residents have to supply income, local and city tax records to extend their visa. Definitely do not see it being asked for at the airport as the OP mentioned.
I have seen one from London, one from USA who were on METVs and got the DTV. On arrival at the airport, one mentioned being asked about the 2 visas and the IO cancelled the METV giving entry on the DTV. Also some on ED visas awarded the DTV before it was cancelled. These posts from last year. Not seen such posts this year.
Anonymous participant You don't have to show income but they can/often request evidence of income via a tax return, payslips or bank statements with income deposits etc.