Travelling to Japan

I’m a 20y/o F looking to study in Korea (exchange student) and I’m really intrigued about the thrift stores there. I know they’re dirt cheap in comparison to places in Europe, for instance, and I wanted to know where the best spots are. I am also looking to travel to Japan for a couple days for clothes hunting. I’m looking to spend around £100 with like 5-6 items of clothing at least.