Following the sudden loss of her father, eleven‑year‑old Momo Miyaura departs Tokyo with her mother for a secluded island in the Seto Inland Sea. Her sole keepsake is an unfinished note that reads only "Dear Momo" and the ache it leaves behind. The missing words echo in her mind, haunting every corner of the island. In the unfamiliar village, Momo hesitates to acclimate to weathered timber houses, hushed fields, and enigmatic lone shrines. While rummaging through the attic of her new dwelling one afternoon, she discovers a tattered volume on yokai. She feels a chill as if eyes watch her. After this find, uncanny events ripple through the town and three mischievous yokai appear to greet her. "Momo e no Tegami" chronicles a girl"s struggle to settle into a new existence amid whispers of and waves, learning resilience and accepting the mystery of the father's letter.