[Nyororin]

First - Matsumoto is a pretty big city. It`s not a little town on the side of a mountain.
I would be extremely shocked if you did not have access to at least 100Mbps FTTH. Even in the mountains you can get fairly fast ADSL (40Mbps+) in most places.

The current situation is that if you have a phone, you can get ADSL. And if you live anywhere in or around a city, you can get FTTH. I don`t know anyone who still relies on dial-up for their internet access. It`s sort of been reserved for 2-way television (modem in the tv dials and sends data) at most providers.

You are going to stand out no matter what color your hair is. If you have black or very dark hair you might, just might, have a chance of not standing out much from behind. But really, your hair color isn`t going to have much of an effect on you standing out.

You should have no extra charges for using your card in Japan. You might want to contact your bank about the fact that you`ll be using it in Japan though, as I`ve heard many stories of banks stopping the card as a safety precaution if it`s suddenly used a bunch in another country.
Grocery stores often don`t accept cards, as well as about half the convenience stores - tiny corner shops are a given... But otherwise, most places accept credit.

Matsumoto is a nice place, spent some time up there last year. The most negative things I can think of about the area is that a large part of the city ends up in the shadow of mountains for part of the year. Depending on where you live, you may only get an hour or so of sun hitting your place a day. This can make winter pretty cold.
As MMM said, you can get good seafood anywhere in Japan. Nowhere is all that far from the water. Even in the middle of Nagano, you can still get to the coast and back in half a day or less. If I recall correctly, it took us about 3 hours to get from Matsumoto to the sea.