Hazuki Fuwa, a middle school student residing with her parents and younger brother Shohei, navigates a life upended when a neighbor’s mention of a bankrupt family sharing their surname sparks her suspicions of financial collapse. These doubts crystallize as her father abruptly orchestrates an opulent family trip despite their strained circumstances. His uncharacteristic joviality and reckless indulgence in costly excursions deepen her alarm, convincing her the outing masks a grim intention: a collective family suicide.

Her dread solidifies upon discovering coiled ropes and hoses in their car, which she interprets as implements for carbon monoxide poisoning. Throughout the trip, she maintains a watchful guard, agonizing over her private diary—filled with candid reflections on her crush, Aisaki—and its potential exposure posthumously. The crisis peaks when her father steers their vehicle off a cliff, only for the family to survive by plunging into a snowdrift. A subsequent collapse from food poisoning unravels her father’s desperate rationale: a terminal misdiagnosis had driven him to orchestrate their deaths to spare them future destitution.

Post-incident, the family relocates and embraces a frugal existence, Hazuki’s mother securing part-time employment. Their priorities shift toward modest joys like shared picnics over lavish excursions. Hazuki’s journey traces her evolution from spiraling paranoia to confronting her family’s concealed hardships, culminating in a hard-won resolve to value resilience and pragmatism in rebuilding their lives.