I will pick out some reasonable clothing brands in Japan below.
These are Japanese company’s brands and selling both men and women clothing.
(There are much more brands for women. Sorry, I have a no idea about it.)

　　They are divided to three groups by their shops locations.

1.　Close to stations
　　You can find these shops in buildings close to big stations.　

　

　　Fastfashion Brands

　　・UNIQLO （* Upper URL ; Online Store, Lower URL ; shop search）
　　　　　https://www.uniqlo.com/jp/ja/
　　　　　https://map.uniqlo.com/jp/ja/

　　・GU（subsidiary of UNICLO）
　　　　　https://www.gu-global.com/jp/ja/
　　　　　https://map.gu-global.com/jp/ja/

　　・WEGO
　　　　　https://wego.jp/
　　　　　https://wego.jp/a/shops

　　・Right-on
　　　　　https://right-on.co.jp/
　　　　　https://biz.right-on.co.jp/english/shop/

　　・GLOBAL WORK
　　　　　https://www.globalwork.jp/
　　　　　https://www.dot-st.com/globalwork/info/storelist/

　

　　Selling household items and clothing
　　・MUJI
　　　　　https://www.muji.com/jp/ja/store
　　　　　https://www.muji.com/jp/ja/shop?area=footer

　

2.　Not central,
　　You can find shops close to stations which are at the edge of Tokyo.

　　Outdoor wear
　　・Workman Plus
　　　　　https://www.workman.co.jp/store/property/workmanplus

　　”Workman” is brand selling working clothes for men, such as carpenters. They have started new-brands “ Workman Plus” and “Workman Jyoshi which is selling clothing for women. (Jyoshi means women.)

　　One of Workman Jyoshi shops is in Ginza.

Address : 〒104-0061 東京都中央区銀座五丁目7番10号 中村積善会ビル内5階
　　　　　https://www.workman.co.jp/store/property/workmangirl

　

３.　 Surround Tokyo areas

　　Outlet Shopping Malls
　　It takes a couple of hours drive from Tokyo though, you can get to some of them by train.

　　・Mitsui Outlet Park (One of them is close to Makuhari Messe.)　
　　　　　https://mitsui-shopping-park.com/mop/english/

　　・Aeon Lake Town Outlet
　　　　　https://en.aeonmall.global/mall/laketown-outlet/

　　・Premium Outlet
　　　　　https://www.premiumoutlets.co.jp/en/

　

　If you are interested in fashion trends in Japan, check it up!