Nakano Broadway Mall is a large, mostly indoor shopping mall that is known as a sometimes cheaper (but often not) alternative to Otaku paradise Akihabara. You’ll find many Anime, Cosplay, Doll and a few Game shops. The famous second hand anime, manga, game, doll, idol, cosplay, retro toy chain Mandarake (http://order.mandarake.co.jp/order/) has quite a few stores here. Be sure to take your time and explore all the floors. While most anime, manga, game shops are located close together, there are a few hidden around the place.
On the first floor you can find local, traditional shops, restaurants, clothing shops and a second hand electronics shop called Junk World.
After you’re done browsing the inside, go out and explore the shops leading up to the indoor mall. There’s Karaoke, lots of restaurants, camera shops (fujiya-camera.jp), KuroNeko maid cafes (in japanese: http://www.necomimi.info/cafe/) and even an anisong (“anime song”) karaoke bar called Anison Karaoke Bar Z (http://www.anisonkaraokebar-z.com/), which yes, is a bar not room, so be prepared to sing in public!
Beware! Lots of shops are closed on Wednesday so be sure to go some other day. I’d recommend weekdays as it gets really crowded in the weekends.
Nakano Broadway is the perfect place to spend a rainy day, or frankly any other day than Wednesday. Getting there couldn’t be easier as it’s right next to Nakano Station.
Official website: http://www.nbw.jp/index_e.html