Where to find ridiculously cheap clothing?

Last week, I visited Kobe, I went to some sort of shoutengai, near a chinese town.

Out of pure luck, I stumbled upon a clothing store (I though it was 中古 but they were selling new items.) inside the shoutengai. I went inside and they were selling 13,000 JPY price tagged skirt for 50 JPY. (3,500 JPY before that) and I saw many good clothing pieces for ridiculous numbers like 50 JPY, 100 JPY. for full blown sweatshirts, tight miniskirts with proper and quality fabric stuff. I couldn't believe my eyes.

What do these stores called? Where can i find such stores in Osaka?
Is there a similar but electronics version of these kind of stores?
Any specific stores you know of in or around Osaka?

by exivor01