Hello everyone!

I have a question about the I-130 and other immigration forms. My fiancé wants to list her step-father as her father on the forms but I am unsure if this is correct. When I see a request for her fathers name I think it is her birth father but I am unsure. Maybe it is different in Japan since she is Japanese.
Which should I use?

Thanks!

use the name of her father which is mentioned in her important documents
like her passport and her certificates
you question is not that major issue dont worry
she can always mention about the ex - father in her interview