Michiru is a high school boy who isn't particularly good at anything, including sports and socializing. He enjoys watching one of his classmates, Haruka, as she practices swimming. Haruka happens to be the only member of the swimming club associated with his school. As she and the coach search for new members, she notices him and innocently assumes he's been watching her because he really wants to swim. Michiru is unable to refuse her invitation to join the club, even though he has never swum before and has no idea how it's done. Michiru finds his life changing as Haruka patiently teaches him how to swim.