A-Channel revolves around the complex friendship and relationships between Tooru, Run, and their classmates at high school. Tooru's excitement about attending the same school as her lifelong friend Run is short-lived when she discovers Run with a new girlfriend, Yuko. This development creates tension, particularly as Tooru navigates Run's relationships with Yuko and another girlfriend, Nagi, amidst Run's propensity for dramatic situations. The dynamics among the group add a layer of complexity to their high school experience.