Don't talk about your ex’s
What not to do when dating a Japanese woman?
When it comes to a relationship with a Japanese women, talking about an ex is like walking directly into a minefield - apply the "don't talk about your ex" rule. Period.
First, they hate hearing you talk about your ex, not because they are egoistic, but because they see this as a basic lack of respect.
Also, jealousy is a really delicate issue with Japanese women. It has always seemed to that they tend to get more jealous than western women. It might be because, in Japan, they don’t have so many friendships between the sexes. Japanese people tend to stick to their own gender. So you always have to be a careful if you have female friends, she might get jealous.
Let's be honest here, when you talk about your ex-girlfriend, you are making it harder on your new Japanese girlfriend. In general, guys are being honest the ex-girlfriend, but the reality is your new partner might get annoyed by it. I know I would.
It is a major turn off for a Japanese women when their boyfriend talk about their ex. Don't compare your partner to your past relationships, it makes them sound like they are still in love with them.
The past is the past, if you have the need to talk about your ex to you present partner, maybe something is not completely healed.
Remember, it's a sign of maturity to let the past be the past.