Best to prepare thoroughly as they will ask questions about your lesson plan, which you will have to complete and submit before, but overall, a very straightforward and professional interview.
I applied online. The process took 4 weeks. I interviewed at Westgate
Interview
There are phone interviews with the HR staff and you're required to complete a sample lesson plan. The lesson plan is written and sent to the HR staff who reviews it.
Interview questions [1]
Question 1
Create a lesson plan for a listening/speaking class
Roughly 60 minute interview going over various reasons of why I wanted to work for Westgate, why I wanted to work in Japan, answering questions related to my CV and finally English language related questions to prove my competence as a teacher.
Interview questions [1]
Question 1
Why do you want to work in Japan?
Various grammar questions and role playing error correction scenarios.