Utsumi So (Takasugi Mahiro) does not have many friends or any high school club activities. He would spend his free time before going to cram school idling at the riverside. One day, Seto Shokichi (Hayama Shono), who has too much time on his hands after dropping out of the soccer club, shows up. Despite being polar opposites in character, Utsumi and Seto find common ground on one point – killing time. And so, they would chat idly as they spend time together at the usual riverside after classes.