I have booked Granvia hotel for my stay in Osaka, but I really wanted to book IL CUORE at Namba station. This hotel is within my price range, and seems to be perfectly located for my plans. We are arriving to Osaka from Koyasan, so the hotel should be very close to Namba station. I found the website. It is all in English, but the reservations are in Japanese.
http://www.ilcuore-namba.com/en/what/index.html
I tried to e-mail them several times, no answer.
I think I can book them via asiarooms or orbits, but the prices are higher than on hotel website, they want a prepayment, and charge fee for cancellations.
Any suggestions?

You'll probably have to reserve using their online form in Japanese if you want that rate...often even if you call they will not give you the internet rate. You could try faxing and giving them a time that you will call to confirm your booking and rate, but that may not get you internet rate. You have found with this hotel what is pretty normal...best rates directly and in Japanese.

Use the "Contact us" button on the hotels website requesting the reservation.
When we stayed there we requested a twin room because the double rooms are smaller.

Clark, I used 'Contact us' button. This gave me their e-mail contact. I e-mailed requesting a reservation (tried 3 times) - no response.

I think they haven't realised that there's something wrong with their English booking system, either that or they've removed it We booked directly with them through the website & it was possible in English. Your only other option will be through a reservation agency such as you've already named although here's a lot more than asiarooms or Orbitz you might find something cheaper on another one. You'll have to spend a bit of time checking them all out but it's either that or find someone who knows Japanese to help you book it through their website.

Thank you, Kim! Thank you, Clark!

It is so frustrating...