I saw a program last year on Japanese TV where he photographed kids with a large format camera (don't know enogh about LF to id the setup).
In front of me I have Vol. 05 Winter 2006 issue of the Japanese magazine Photo Graphica. It features Homma and shows his cameras: Minolta TC-1, Leitz Minolta CL (Pic too small to read from the lens, but it looks like the 40mm summicron), Polaroid 690, Makina 67 (I think the text states is in use for around 20%) and finally a Linhof Master Technika 45 Classic - can't make out the lens (this camera is in use around 80%).
I also have the diaries with the GF670 reference above. He may use the product but it is a paid product placement.