ef unfolds through two intertwined romances that test how memory shapes love, identity, and the choices people make. On Christmas Eve, Hiro Hirono meets the impulsive Miyako Miyamura after she "borrows" his bicycle to chase a purse thief; when he finds the bicycle wrecked and Miyako unconscious, the two unexpectedly spend the night together, and their accidental bond deepens after they realize they attend the same high school. That closeness sparks the jealousy of Hiro's childhood friend Kei Shindou, whose sincere approach to life also catches the attention of Kyosuke Tsutsumi, a womanizing photographer searching for the perfect shot.
At the same time, Renji Asou, a boy who dreams of being a girl's knight in shining armor, crosses paths with Kei's twin sister Chihiro Shindou, the painfully shy girl who spends her time reading alone, at an abandoned train station. The two quickly become friends and eventually decide to write a novel together, but when Renji discovers Chihiro's secret, his childish ideals are put to the test.
Guided by two mysterious adults, these young people's relationships intertwine in a heart-rending story of love, rejection, acceptance, and the memories that linger long after each choice.
