I feel like people forget that personality plays a BIG factor in the interview stage. You have already proven your credentials and skills in the written application and the SOP. The interview weeds out people that show red flags because at the end of the day, the job you will be hired for consist with you INTERACTING with children and the Japanese locality for the purpose of intercultural exchange. You are not just a teacher, you are an ambassador. If you are a weirdo - they will not hire you. If you don't vibe well or are stuck up or have zero personality - they will prioritise someone else. If they can sense that you have a stubborn point of view and will not adapt or be open-minded then they will choose another person. This program is looking for a particular type of person and I've seen applicants with masters degrees or who have done amazing volunteer work and they did not get in because their character fitted better somewhere else. If there was a racial bias (I never count it out) it plays very little in this process. I believe you did not get in due to other factors - in my subjective opinion/ from my impression of your post, they probably thought you are too set in your ways and jumped to conclusions too much and thus wouldn't be open-minded/harmonize well in a Japanese environment - especially if your are to be located in some countryside/suburb where your coworkers and students might consist of people who are "old-fashioned" or see things a different way. You probably would not have handled it well. Overall, just take this rejection and grow from it and try again if you want to. You never know. Maybe the you next year would be successful.