I went to the Aeroplaza Lounge pre-flight last week. I got my boarding pass first, but when I got there they said just a digital version showing you are flying out that day would be okay.

Used Rakuten Priority Pass. PP gets you a three hour stay plus two choices: one food or 2 beers/chuhai or shower

Japanese Gold cards (like DC) will also get you access to the lounge for 2hrs, with free non-alcoholic drinks.

Plan on it taking 5-10 minutes to walk from Aeroplaza to Security, so best to leave at least 60 minutes before boarding.