Sing a Bit of Harmony tells the story of Shion, a beautiful and mysterious girl who transfers to Keibu High School and quickly becomes popular due to her open-hearted personality and exceptional athletic ability...until she is revealed to be an AI in the testing phase! Shion's goal is to bring chronic loner Satomi "happiness," but her strategy is unexpected: she serenades Satomi in the middle of the classroom. Satomi and her childhood friend, engineering geek Touma, gradually warm up to Shion after learning that he is an AI. Shion's singing and earnestness move them, along with the popular and attractive Gocchan, the strong-willed Aya, and judo club member "Thunder," even as her antics irritate them.