Which stores should I go to buy watches in Japan?

If you buy an ordinary watch, yodobashi or biccamera will do.

The rest depends on fate.

There are two kinds of watches bought in Japan, one is licensed in Japan, and the other is parallel (that is, licensed elsewhere, which is commonly known as "parallel"). Parallel input is legal in Japan.

Among the parallel watch shops in Tokyo, there are four famous ones, commonly known as "Four Temples", namely Jackroad, Kamiji, My Watch and Gem Plaza (in no particular order). Two of them are in nakano, very close.