It is the year 2027, and the city of Kyoto has seen tremendous technological advancement. Two classmates live within the city: Naomi Katagaki, a socially awkward and introverted boy; and Ruri Ichigyou, a girl with a cold personality who is often blunt with others. Although Naomi shares Ruri's love of reading, he is afraid to approach her because of her unfriendly nature. One day, while out for a walk, Naomi witnesses a crimson aurora briefly pierce the sky before vanishing. Shortly thereafter, he encounters a three-legged crow and a mysterious hooded man, who reveals himself to be Naomi from 10 years in the future. He explains that he has come to alter an imminent tragic event that befalls Ruri soon after they begin dating. Initially skeptical of his words, present-day Naomi follows his future self's instructions and begins to get closer to Ruri, determined to save her. Will he be able to change the future?