Jin Kikuchihara is a third-year student at Midorigaoka Boys' High School, the charismatic and narcissistic president of the film club. He is handsome, athletic, academically gifted, and loves being the center of attention. Giichi Ichikawa, a second-year in the same club, is a talented and exacting director who constantly clashes with Jin, treating him as a rival. Their mutual animosity is a running tension within the film club, but underneath the bickering, each is acutely aware of the other.

Their dynamic is forced to change when a family situation leaves Giichi without a place to stay, and he temporarily moves into Jin's dorm room. Forced to share close quarters, the two establish a fragile truce that quickly breaks down their antagonistic facade. Jin is surprised to find that Giichi, away from the club, is not the hostile person he expected, while Giichi begins to see past Jin's flashy exterior. Their constant bickering gives way to a reluctant attraction and, eventually, a deep, awkward love. The conflict shifts from their rivalry to the vulnerability of navigating their new feelings, the pressure of approaching graduation, and Jin's need to decide who will succeed him as film club president.

The original narrative arc covers the beginning of their relationship, from forced cohabitation and mutual realization of their feelings to their first steps as a couple. A subsequent continuation arc, sometimes labeled Afterimages in Slow Motion 2 or as a new chapter, follows them after they have become boyfriends. Jin, now graduated and in university, struggles with the demands of a campus festival, while Giichi, now the film club president, grapples with the pressure of filling Jin's shoes. Their limited time together and the looming threat of growing apart lead to a spontaneous train ride and a shared vow symbolized by rings, affirming their commitment to a future together despite the changes that come with graduation and the end of their school days.