A letter from your future self arrives telling you to save a boy you've never met, and the show spends thirteen episodes proving that sometimes the smallest choices matter most. The romance isn't a prize you earn, it's the thing you're trying to protect, which means every conversation carries the weight of knowing what you're fighting to change. Naho's attempts to rewrite fate keep collapsing into the same small heartbreaks, but she keeps trying anyway, and that quiet refusal to give up is what stays with you.

Naho Takamiya is sixteen and starting a new year of high school when a strange letter reaches her. It claims to come from her own future self, ten years older, and it describes events that are about to happen. The letter urges her to keep watch over Kakeru Naruse, a transfer student joining her class, and warns that in her future he is gone. Doubtful at first, Naho begins to notice things the letter predicted. Her older self is full of regrets and hopes the younger Naho can undo the mistakes made along the way. With the letter as a guide, Naho must weigh her choices around Kakeru carefully, knowing they could shape both his future and her own. The story mixes teenage romance and drama with a supernatural twist.