Depends on what style are U and how old are U
I like trendy, chic and sexy outfits for night out. So, "Maru-Kyu" or PARCO 109 is awesome !!! I forgot what floors they have, but all the trendy japanese girls shop there. U can find everything there, just name it and the price is pretty reasonable for japanese market. Go to Shibuya and Shinjuku. Harajuku is like the hippies, very funky, rock n roll, everything, reminds me of London.
Check out this brand: SLY, MOUSSY...... they have cute jeans, tops, etc. The hottest Jap brands. But YES, Japanese run so SMALL. Only S and M for tops. Jeans basically can run 1 size smaller. Size 27 there, is like 25-26 US jeans. So, beware. Also japanese shoes run small, their feet mainly around size 6 or 7 the largest. So finding size 8 and above kinda hard.
I love makeup station in underground the subway. SO MANY to choose and so cute. I love KATE by Kanebo. their eye shadows are great, long lasting, cheap, and it's like Stila in here or better. Very cute. Get De-Ja Vu mascara, this mascara worksss !!!!