Wani is an anthropomorphic crocodile living an ordinary life, unaware his death is predetermined to occur in exactly 100 days. He fills his days with routine activities: working part-time, eating ramen, playing video games, watching movies, and playing basketball. His world involves typical interactions and modest pursuits, including visiting friends in the hospital, maintaining phone contact with his mother (who sends him mandarin oranges annually), and harboring romantic interest in a coworker.

He shares close bonds with several animal companions: his best friend Nezumi (a rat), Mogura (a mole working at a recycle shop), and a senior colleague known as Senpai at his workplace. His social interactions emphasize simplicity and warmth, often lightening moments with humor, like using favorite one-liners to cheer Nezumi during hospital visits.

The narrative culminates at a cherry blossom viewing party, where Wani unexpectedly vanishes. His absence prompts Nezumi to search, leading to the discovery of Wani’s cracked phone on a roadside. The phone displays a photo of cherry blossoms Nezumi had just sent to friends, confirming Wani’s death on the 100th day.

Following his death, Wani’s friends experience profound grief, gradually distancing themselves from each other due to unresolved sorrow. Months later, the arrival of a new character, Kaeru (a frog), intensifies their struggle to reconcile Wani’s absence. Kaeru’s assertive personality inadvertently highlights the irreplaceable void left by Wani. The story underscores themes of impermanence and the quiet significance of everyday existence through Wani’s unremarkable yet impactful life.