With university entrance exams looming, high school senior Mihane Yoshiyama is feeling the pressure of her impending future. A member of her school's photography club, her life takes an unexpected turn just before summer vacation when she passes by the science lab after class. There, she is enveloped by the distinct aroma of lavender, an experience that inexplicably grants her the ability to leap through time.

As Mihane begins to navigate this newfound power, she finds herself drawn closer to her classmate and supposed childhood friend, Shohei Fukamachi. However, Shohei is not what he appears to be. He is actually a brilliant researcher from the year 2122 who developed a drug capable of enabling time leaps. Having used the drug to travel to the year 2016, he lost it and is now stranded in the past, unable to return to his own era. To blend in while searching for a way back, he has hypnotized those around him into believing he is an ordinary high school student.

Over the course of a few intense summer days, Mihane and Shohei grow closer, their shared secret forging a powerful bond as romantic feelings begin to develop between them. Their connection is complicated by Shohei's origin and the knowledge that his time in the present is limited. The series follows Mihane as she experiments with her ability to leap through time, exploring the wonder and consequences of altering moments, while also unraveling the truth of Shohei's mission and his past. As their relationship deepens, they must confront the painful reality that the memories they are creating may be fleeting. In the end, the romance that blossoms lasts only a few precious days before Shohei must find a way to return to his future, leaving Mihane with a fading memory of a boy from another time.