Just saw how crazy 2nd street expanded in Japan. Also, it shows so much stuff at a store. I know 2nd street and others give Japanese so little money compared to Mercari. Like Rip off prices...10-15% of value?
Or is some items sourced from outside Japan?

I see lots of tourists going crazy at those stores but the items are in good condition but they charge as much as new for US residents.

The only other alternative is to use japanese mercari. There are sites like Buyee that sends to your country. But I think some package forwarders will hold the package until next time you come to japan and they just ship domestically to your hotel?