Hey Pedro,
There are a couple of dive shops in the area that have english-speaking staff. I think this website is a helpful starting point:
Kansai Diving. I actually met the owner of Mako Dive on a recent trip to the Philippines and can confirm that he speaks pretty good English.
As for the local diving, my understanding is that the closest decent diving is in the Wakayama peninsula about 3 hours by train/car from Osaka (3:30 from Rokko Island). Because it's bathed by the same Kuro current that flows through the Phillipines and Okinawa, water temperatures get up to 28, 29C in the summer and never really fall below 16-17C. So you get some coral reefs, etc.
However, given that it's a 3:30 hour drive to get there, and given that the costs for boat diving are pretty high, it's certainly also worth looking into Okinawa for diving getaways. Flights from Osaka to Naha can be had quite cheaply now with the new discount airlines and are only 2 hours long.
Once you're in Okinawa, Japan-diver can take good care of you. I've dived with his shop (Reef Encounters) before and had a good time. You could also head across to the Kerema islands (there's a few dive shops with English-speaking staff on Zamamijima and Akajima) -- they tend to dive the same sites as the boats out from the main island of Okinawa, at similar prices, but the advantage is shorter boat rides and nice relaxing island-villages for more of a tropical vacation feel (I didn't find Naha and Chatan, where Reef Encounters is based out of) to be particularly nice areas, though I understand the northern part of Okinawa island is less urban/developed.
Either way, I think you'll find the diving available in Japan and the surrounding areas very nice!
Feel free to send me a PM if you want more details. I actually live very close to Rokko Island.
I may be moving to Rokko Island near Kobe. I checked the PADI site and it lists eight 5-Star Career Development, eight 5-Star and lots of regular dive shops nearby. Does anyone know any of the dive shops in the area? Are there any that speak English?
I will be using Crown Relocators so I can pack as much gear as I want (with the exception of forbidden items). Should I ship my two steel 130s, two steel 72s and aluminum 40 pony? Will a dive shop in Japan fill US cylinders? I suspect that fills and inspections might be an issue.
Is Osaka Bay worth diving? I saw some photos on the dive shop websites and it seems like they are diving the dam above Osaka. Is that a common dive site?