The Gym, named "K3 Box & Fit Gym" is a state of the art gym Setagaya, Tokyo and features 2 floors of fitness equipment, an Oxygen chambers and a tanning booth as well as lockers and personal training and boxing training.
At the moment the gym has merely had it's pre-opening show though it's meant to open properly on March 1st.
The membership fees and other details are featured on the official "K3 box and fit gym" website which can be found here: http://www.k3box-fit.com (sadly for our non Japanese speaking readers the navigation of the website may be problematic).
We would assume that if the Kameda's wanted to be self promoting in the boxing world then there is a big chance that it would be under the "K3" banner rather than the "Kameda Bros." name. This is speculation on out part but it could well make sense considering their appeal for a re-hearing has been turned down.
(Picture courtesy of http://www.k3box-fit.com)