Marie is a grey American Shorthair cat adorned with distinct black stripes across her head, cheeks, back, and tail, featuring almond-shaped eyes. Her nature is gentle and quiet, marked by deep care for her kittens. She maintains constant vigilance over her children during their daily routines.

During a routine walk with her kittens—Ann, Terry, and Chi—Marie loses Chi when the kitten becomes distracted and separates. Following this, Marie dedicates her nights to searching for her missing kitten while continuing to care for Ann and Terry. She keeps this search private, never revealing to her remaining kittens who she seeks.

Marie eventually spots Chi in a park, but Chi flees before Marie can confirm her identity. Marie follows Chi to the Yamada family's apartment, entering their backyard. During this encounter, she definitively recognizes Chi but realizes her kitten no longer remembers her. Marie leaves silently, deeply saddened.

In a later park encounter, Marie calmly approaches Chi, attempting to stir her memory. This interaction is interrupted when Yohei Yamada takes Chi away. During another outing, Marie witnesses Chi darting after a ladybug into a street and into the path of an oncoming car. Marie pushes Chi to safety but strikes her head on a concrete curb, losing consciousness. Before fading, she pulls Chi close and expresses relief at her safety. The sound of Marie's heartbeat triggers Chi's memory of her mother.

After being taken to a veterinary clinic by the Yamadas, Marie recovers fully. She awakens next to Chi, embracing her before they fall asleep together. Marie and Chi are returned to Marie's original owners, reuniting with Ann and Terry. Life resumes its normal pattern for the feline family.

Marie learns from another cat, Blackie, about the Yamadas' impending move to a distant location. She privately asks Chi if she wishes to leave with them, emphasizing the decision rests solely with Chi. After Chi confirms her choice to depart, Marie initially shows disappointment but accepts her daughter's decision. During the family's routine park outing, Marie instructs Chi to "quickly go home," with Terry and Ann cheering their sister on. Marie watches as Chi runs toward the Yamadas, disappearing into the distance.

Marie shares a close bond with all her kittens. Her relationship with Chi is defined by persistent search efforts and ultimate respect for Chi's autonomous choice. She demonstrates consistent affection and care toward Ann and Terry throughout their shared experiences. Marie also develops a deepening connection with another cat named Cocchi over time.