Who is Zhen Zi's father?

There are four novels about The Ring of Midnight. Sadako Yamamura's father is Dr. Ixiong Hirashiro. The novel is Dr. Ichio Hirashiro, which is a little different from the movie. But Ixiong Hirashiro is just her adoptive father. It seems that in the second film, the old man in the village who was with Mako's mother said that Shizuko gave birth to the movie "To True White", and Dr. Ichio Hirashiro said, "Mako slowly split into two people, one like her mother and the other like her mother. There is still a big gap between novels and movies.