Ok I love when people ask about the best places to come in Japan I have had so many family members and friends come to visit the I set up a free web page to put all the information I had to email them in one place
Check out
Japan Travel info in English
I still have more stuff to add on it but I think it will give you some insight for you 4 day stay in Tokyo and I agree with one of the previous posters you don’t have to visit Tokyu Hands it really is nothing special unless you come from some remote out post and have never see a craft / stationary store before.
Any ways good luck in Tokyo