"There are three massive Japanese motor brands - Lexus, Honda and Nissan fighting it out in a 15-car field for the Japanese championship.
"Each region has their premier GT category. There is DTM in Germany and Supercars in Australia - this is it for Japan."
The Super GT Championship is well regarded around the world and there is likely to be significant interest in Cassidy's services but he is not planning on any big changes to his 2018 program.
"I have thought about it a little bit but at the same time I have been so focused on finishing the year strongly and getting the championship done that it hasn't been a massive priority," he said.
"I am pretty certain I will be in the same situation next year with Lexus and trying to defend the championship - I am 90% confident of that but nothing is confirmed for sure."
Cassidy split his time this year by running in the premier Japanese single-seater category as well and narrowly missed winning that title.
"It looks good that I will be staying in Super Formula again and do a dual program next year, which I think is really important.
"Firstly it is really fun to drive the fastest cars in the world basically and then secondly to be racing that much in Japan - seat-time is really valuable as well."