In a world that closely resembles reality, there lives a seemingly ordinary girl named Kuroi Mato, who begins her vibrant and brilliant middle school life in the new year. At this time, a classmate named Takanashi Yomi catches her attention. Initially, Yomi shows no desire for deeper interaction, but later, due to a conversation about rainbow-colored birds, Mato witnesses Yomi's vulnerable side when she is wronged... In a bizarre world, a group of people live under a sky as blue as tears, engaging in covert and overt struggles every day like warriors, as if bearing the troubles and chaotic thoughts encountered by others...