Good news: As of this month, YahooBB finally serves Nita-cho! Mr. Internet stopped by the Nita BoE this afternoon, and we went over to his office to fill out the forms online.
Less-than-good news: They're slower than winter molasses to get it running. It will take 28 days. I'm supposed to get another form in the mail, fill it out, and return it, after which time I will be sent a modem, and presumably my internet connection will be activated. But I don't know if it will be 28 days until I get the Something in the Mail, or 28 days until the action starts.
But YahooBB was the ISP I'd wanted even before I arrived in Japan, if only because their internet phone service allows me to place 3 yen/minute phone calls to the US.
Right now, I'm high as a kite (in a purely psychological, non-medicinal way).