When Marnie was two years old she moved with her family to the Marsh House in the seaside town of Kissakibetsu. She was often mistreated by her nanny, Georgina Gordon and the maids, Ursula and Ella while her parents were traveling. Eventually, she met a man named Kazuhiko. Kazuhiko and Marnie spent a lot of time together, often sneaking out. One day, Kazuhiko and Marnie went to the silo that Marnie was deeply afraid of, due to the maids' usage of the location to secretly abuse her. She nearly died while in the silo, before Kazuhiko saved her.
After Marnie grew up, she moved to the city of Sapporo, married Kazuhiko and had one child, a daughter named Emily. While Emily was still a young child, Kazuhiko died of an unknown illness. The shock of his sudden death caused Marnie to fall into depression, and subsequently resulted in her having to be institutionalized in a sanitarium for some time. Marnie's parents had since passed away, and Kazuhiko's family was never mentioned, thus, Emily was sent away to boarding school. Years later, Emily (said to be 13 at the time) returned to her mother's care. Marnie greeted her daughter with open arms, expecting a hug, but Emily just walked past her and got into the car without a single word as she had strong feelings of anger towards her mother due to her perceived abandonment.
Marnie and Emily's relationship was never salvaged and when Emily was a young adult, presumably in her late-teens or early-twenties, Emily ran away from home after having once last argument with her mother to marry the man who had gotten her pregnant with. Marnie was not informed of her daughter's marriage of the birth of her grandchild, Anna. When Anna was two years old, Emily and her husband were killed in a car accident. Marnie took Anna in and did her best to care for her and make sure her granddaughter could never feel alone but she never recovered from Emily's death. Unfortunately, Marnie fell ill and passed away when Anna was still a toddler. Anna was then placed in either an orphanage or foster care, where she was taken on and possibly adopted by Yoriko and her husband at the age of five.
After Marnie's passing, her spirit returned to her hometown, mainly to her childhood home and the abandoned silo. The townsfolk eventually noticed her presence and avoided said places.
When Anna was forced to go to the seaside town that Marnie grew up in, she re-lives some of Marnie's memories with Marnie herself (who made herself look like her preteen self) taking the place of Kazuhiko in (most) of the memories. Anna seemed aware of the fact that Marnie was a ghost but she didn't show any fear towards her and their time together helped Anna to become less introverted and more willing to open up to people.
Marnie has long, blonde hair that falls over her back, ending is smooth ringlets. She wears her hair loose for most of her screen time, wearing a blue dress with white frills and a blue ribbon tied at her collar and also wears a green dress with a yellow bow on her collar. She wears at one point a white nightgown with a blue ribbon on her collar and goes barefoot.
At the party, she wears a pink dress with various frills and high heels. Her hair is held in an elegant-yet-simple style, having only one portion held back with a matching ribbon. She sports red earrings.
As an adult and old lady, her clothing is much more simple, having a warm, earthly look.
- Unnamed parents (deceased)
- Kazuhiko (husband; deceased)
- Emily (daughter; deceased)
- Unnamed son-in-law (deceased)
- Anna Sasaki (granddaughter)
- Marnie look similar to Odette from The Swan Princess series also in the 9th film she met Anna Sasaki same like Princess Mei Li have met.
- Her birthday is July 15th.