It looks like Horiuchi Color no longer processes film, they're all digital now. I'm sorry I can't help you with Osaka or Nagoya as I'm stuck in the middle in Kyoto, but whenever I need slide film developed I just bring it to Yodobashi Camera. I don't know if they do it themselves or send it out, but I don't have any complaints. The only thing is the turnaround - can be a couple days up to week, depending on when you go (weekends and holidays will extend things a bit) and what you are getting done (film, size, mounts/prints, etc). The Yodobashi in Osaka might be faster, but you never know. When I lived in Kumamoto a few years ago, I could get slides done in 2-3 hours (35mm or 120) and B&W film done in 24 hours. I haven't found any place like that yet here in Kyoto.