Haruna Yu (voiced by Yusuke Kobayashi) is an ordinary boy who has just moved to Tokyo. He is very introverted and can only rely on his mobile phone to express his thoughts. Therefore, in the eyes of outsiders, Haruna Yu is a "head-down tribe" who holds his mobile phone all day long. By chance, Haruna Yu met a girl named Akizuki Fuuka (voiced by Lynn). Unlike herself, Fuuka didn't even have a mobile phone, which made Haruna Yu feel very incredible. Fuuka is the lead singer of the band "The Fallen Moon". At her invitation, Haruna Yu joined the band and became a bassist. A naive relationship slowly brewed between the two. At the same time, Haruna Yu reunited with his childhood friend Hibiki Koyuki (voiced by Saori Hayami) on the Internet. Koyuki has now become a famous idol singer in Japan.