A teenage boy meets himself ten years older and learns he has three months to save the life of someone he hasn't even met yet. The movie doesn't waste time on paradox mechanics, it uses time travel as an excuse to ask whether you'd actually change your own past if you could, knowing what it costs. By the end, you're not thinking about the plot. You're thinking about the person sitting next to you in the theater, and whether loving someone means protecting them or letting them become who they're meant to be.

In 2027, Kyoto has become a city of advanced technology, and Naomi Katagaki is a shy, introverted high school student there. He shares a love of books with his classmate Ruri Ichigyou, but her cold, blunt manner keeps him from approaching her. After he sees a crimson aurora flash across the sky, he meets a three-legged crow and a hooded man who says he is Naomi from ten years in the future. The older Naomi has come to prevent a tragedy that strikes Ruri shortly after the two begin dating. Doubtful at first, the younger Naomi follows his future self's guidance and starts growing closer to Ruri, hoping to save her. The film is a sci-fi romance with psychological drama.