Didn't travel far!
Logistics going further west looked a bit difficult (lack of shops near the forest police campsite) and in the end we opted to head back to Naze and stay in the hostel again, dying out our tents on their roof!
We tried to buy ferry tickets to Kagoshima at the port a couple of times. First time, in the early afternoon, there was not much open and we met Miles (?) from the US who is exploring Japan by bike a section at a time. He's fluent in Japanese having learnt it at school and been based near Tokyo as a marine for a few years. He's a lightweight bike-packer on a carbon-framed bike, staying at hostels, hotels and guesthouses along the way - probably super-fast at touring!
The second time, in the evening, the ferry terminal was super-crowded with kids (mainly) waiting to email on the nightly ferry. Although the check-in desks were open, the helpful staff couldn't help us, but did eventually direct us to the main office of the ferry company running the ferry on Saturday evening; there are two different companies, and they run the ferry on alternate days - a job for the morning before we cycle away again!