Anna Sasaki, orphaned in infancy by a car accident in Sapporo, entered her grandmother's care only to lose her the next year. With no immediate family, she was sent to an orphanage, her sole possessions being her grandmother's blue hairclip and an old photo of her grandmother's childhood home. Adopted at age five by Yoriko and her husband, she experienced a generally happy childhood. Around age twelve, Anna discovered government documents revealing financial support for her care provided to her adoptive parents. This led her to question their affection, believing it financially motivated. She emotionally distanced herself, calling Yoriko "Aunty," and became withdrawn, socially isolated at school, struggling to connect with peers. These feelings of alienation, compounded by unresolved grief over her biological family's loss, fueled anxiety and depression. A school asthma attack resulted in medical intervention and relocation to the rural seaside town of Kissakibetsu to live with relatives Setsu and Kiyomasa Ōiwa for cleaner air and stress relief. In Kissakibetsu, Anna explored an abandoned mansion across a salt marsh, feeling an inexplicable familiarity. Trapped by the tide during one visit, she was rescued by local fisherman Toichi. She began having vivid dreams of a blonde girl in the mansion. Following a confrontation with local girl Nobuko at the Tanabata festival, Anna fled to the marsh and physically encountered the girl from her dreams, Marnie. The two formed a secret pact of friendship, meeting privately at the mansion. Anna confided her feelings of worthlessness, her belief her adoptive parents didn't truly love her, and her resentment towards her biological family for dying. Marnie shared her own experiences of neglect and abuse by caretakers while her wealthy parents traveled. Anna helped Marnie confront her fear of a nearby silo where she had been threatened, coinciding with a severe storm that left Anna feverish and unconscious. Recovering, Anna learned Marnie's full history from elderly local artist Hisako. Hisako revealed Marnie married childhood friend Kazuhiko and had a daughter, Emily. After Kazuhiko's sudden death, a grieving Marnie entered a sanatorium and sent Emily to boarding school, fracturing their relationship irreparably. Emily later died in an accident, leaving a daughter – Anna. Marnie then raised Anna but died shortly after, leading to Anna's foster care placement. Anna realized Marnie was her grandmother and that their interactions represented a spiritual connection across generations, explaining her familiarity with the mansion and Marnie. This revelation facilitated significant emotional development. Anna processed her grief and abandonment issues, forgiving Marnie and her biological parents. She reconciled with her adoptive mother, Yoriko, who openly discussed the government support, affirming it did not diminish her genuine love. Anna began calling Yoriko "Mother," signaling acceptance of their bond. She returned to Sapporo with newfound peace regarding her identity and family history, promising to maintain connections forged in Kissakibetsu.