The protagonist, Saisho Hajime, finds himself stuck in remedial classes despite being on summer break. He shares this fate with Mizushima Asa, a somewhat aloof transfer student who is also on the swim team. Though Hajime tries to be friendly, Asa's responses are cold. Meanwhile, Unno Juuzou, another swim club member, notices Sorayama Natsume from the gardening club and falls for her at first sight. As days pass, filled with remedial classes and casual swim practices, Natsume brings vegetables harvested from the garden and invites swim club members to share a meal, leading to her becoming closer to Hajime and Juuzou but remaining awkward with Asa. Hoping to improve their relationship, Hajime and Juuzou organize a camping trip for the four of them. Asa and Natsume agree to go, but an incident occurs on the way back, marking the start of their hot summer story.