I see from your post that you're an IT professional. Assuming that you will be continuing in the same line of work, you would probably be living in Tokyo and possibly commuting from outside of Tokyo to keep costs low. But in general, the cost of living is a beast here in Tokyo. Think New York City, but more expensive groceries.
As for equipment, I have seen a small barebones set (tank, skimmer and salt) for like $200 or so online, but you'd probably need more than that. I would say a lot of the fish and such in Japan are considerably less expensive than at the LFS near my parents' place in California. But the price on any livestock is significantly more in Tokyo shops than from any southern Japan website. I spent quite a bit on my equipment, but I actually got most of it heavily discounted at a store FAR into the Saitama boonies.
I don't know how much my parents pay for electricity and they probably would exagerate anyway, but only half a month after I had my tank set up here in Tokyo, my electric bill was already at 8000 yen. ($80-ish). Which is about $30 more than my winter electric bills, but I do have to factor in A/C into that as well. It's also higher than the electric bills I paid while living in Washington DC during law school.
I do like that they have a lot of different products in the stores here due to the hobby being very common. I buy natural salt water, since it's just easier for me that way, but most people in Tokyo mix their own from tap water and some solution to neutralize the water. (I have a filter tap, so this concept doesn't bother me so much, but I swear the tap water smells really chlorinated at some of my friends' places.)
The Internet is a great resource here and delivery is super fast to Tokyo. But it'll probably be frustrating here if you're not somewhat adept at Japanese. ^^;; Also, remember that there isn't much of an exchange or return policy in Japan. So do know what you're getting into before starting the hobby here (and before moving out here.

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