The lower deck of the sightseeing boat is accessible and even has a wheelchair toilet. (The blog is in Japanese but you can paste the URL in Google Translate and it will translate the whole page, or you can just look at the pictures. ?)
The website for the sightseeing boat doesn’t explicitly state anything about accessibility, but it did list a discount for disability ID holders, so the above report is likely accurate – though it would be great if the website stated as such!
There are two different boats, so there could be the possibility only one is accessible…
I one checked the guest houses and ryokans of Ine and have not found accessible one. Accommodations in this area are mostly renovated from old fishermen’s’ residences so they are quite small and there are no lifts. I recommend to find a hotel in Amanohashidate or MIyazu.
It is one hour trip from Amanohashidate to the bus stop “Inewan Meguri Hinode”. Tango Kairiku Kotsu offers accessible “non-step” busses. They say if you inform them before you visit there, they may arrange the “non-step” one for you (as not all are “non-step”).
Amano hashidate 9:54 to Inewan Meguri Hinode 10:50