Yes, Corsa Corsa is the place to go if you are very rich and besotted with prominent Italian brand names. But if you aren't, you're more likely to enjoy a visit to Tempra, farther out along the same radial road (Komazawa-dōri) through southwest suburban Tokyo. Tempra sells used keirin frames, and more. (Remember of course that keirin frames have been repeatedly subjected to huge stresses.) However, the only vintage bike emporium I know of is Katō Cycle, in Nagoya (though I've never been there).

If you're looking for a "vintage" frame or bike, it had better be 56 cm or (better) 54 cm or smaller. Larger than 56 cm is vanishingly rare. OTOH a non-vintage but more or less "classic" of 58 cm or above can eventually be found, if you're patient, lucky, or preferably both. There are sometimes fleamarkets of used bikes and their parts, but a major source is Yahoo Auction, whose share in Japan of the online auction biz is similar to eBay's elsewhere.

There are two great opportunities in Japan for the "CV" aficionado. One is ordering a handmade frame (of any size, of course). There are plenty of builders with experience and skills (as recognized by for example authorization to build frames for Keirin), not just the few whose names have made it to Bicycle Quarterly and the like. A lot say little or nothing on the web. (Why should they?) The other is of course riding. There are some pretty spectacular places within reach (even if unassisted by car or train) of central Tokyo, let alone other cities. (And Japan seems to have relatively few sociopathic drivers, and none who are coked up.) To find out more, sign up for "Tokyo Cycling Club" (which isn't a club but just a website, and anything that people care to arrange or ask about via the website; which is free of charge; and which isn't limited to the Tokyo area).