Feel free to ask! I arrived at Terminal 1. I think the actual disembarkation process took about an hour, though I didn't actually leave the airport for at least another hour and a half due to being incredibly frustrated with being unable to activate the Japanese SIM card I bought from a vending machine at the airport. I have still not been able to activate that card and am currently depending on WiFi to access the internet.
Yes, they asked to me show my vaccination card. Yes, they asked me to show my QR codes (immigration and customs-- the yellow and red pages) from Visit Japan Web. They have free WiFi for displaying the codes, but it is more efficient to already have the codes screenshotted for easy access. But before you display those QR codes, you have to display the blue page (former quarantine/vaccination page) from Visit Japan Web. I made the mistake of only screenshotting the top of the blue page, confidently thinking that it would be enough to enter Japan. Imagine my dismay when I was asked to show the rest of the page too!

Thankfully they directed me to the aforementioned WiFi and helped me log into it.
Hopefully we can meet up in Saitama, as long as there's enough places for free WiFi.