Idol, Burning by Rin Usami

High-school student Akari has only one passion in her life: her oshi, her idol. His name is Masaki Ueno, best known as one-fifth of Japanese pop group Maza Maza. Akari’s dedication to her oshi consumes her days completely – until he disgraces himself and Akari’s world goes into a tailspin.
(Canongate)