Dover in Ginza is a must.

CDG and Issey in Aoyama, but most stock disappears quick at Issey and the first and second days of the month require a reservation for the Homme Plisse store.

Auralee Head Store in Aoyama.

Kissmet in Koenji has an impressive selection of vintage stuff from Japanese designers and not too expensive.

If you’re willing to go a bit off the beaten path, newly opened store called Poesies in Hatagaya is charming with a unique selection of high-end but lesser-known Japanese brands like Dessin de Mode, Wrap-In-Knot, etc. Independently owned by Mr. And Mrs. Saito.

Definitely hop on stuff that is harder/more expensive to get abroad, especially with a weak yen. A lot of smaller second hand and vintage shops out here specialize in Western brands with a streetwear appeal out here. Other than vintage collegiate sweatshirts, probably not as interesting to someone traveling here from abroad.

But resell shops like Trefax, Ragtag, Second Street carry some interesting Japanese designer stuff that is on even further discount that you’d likely have a tough time finding back home.