Sorry for the late reply. (We had a glorious weekend in the Pacific Northwest, and we spent it communing with the cherry blossoms instead of in front of a computer screen.)

I do not know the specifics of the Washlet Adapter Kit, but I suspect that you have hit the nail on the head about its function. The connector between the Inax Clessence and the water supply line to the toilet is simplicity itself, but the line to the toilet seat is fairly short for neatness's sake, and the connection includes a T-connector, so I can envision how the routing could be compromised if the toilet's connector is recessed.

Thanks for your response. I will be getting this item when I order my Inax L, later this spring.

OH, I got caught with a duplicate thread. I can usually avoid these :)

This post was edited by enduring on Tue, Mar 25, 14 at 7:08

We had a similar question about installing the Washlet on our wall mounted TOTO toilet. Seems like the part you reference doesn't come with the wall mounted carrier (or there wasn't even a suggestion to order when I ordered on line).
Anyway, we were trying to figure out what we needed and my tile guy suggested we call a plumbing parts online store in New York. He says NY always has the experts. We had already tried questioning some of the other standard plumbing websites with no luck.
So, I looked online and found:
http://www.nyrpcorp.com/
And BINGO!, my tile guy was able to talk to someone who he said REALLY knew his inventory and the parts and what they were supposed to do. I don't know if this company sells INAX but if you want an expert on plumbing parts who you can talk to in person and who is very helpful, I recommend you give them a try. He made a special effort to verify they had the part in stock. GREAT SERVICE and COMPETENT EMPLOYEES - what more can you ask for! I ordered from them and it only took a few days.
Good luck in whatever path you decide on.

p.s. I have no affiliation with this company except as a very satisfied customer.

Here is a link that might be useful: New York Plumbing Specialties - Replacement Parts