Rascal Does Not Dream of a Nightingale

Book 11 of the Seishun Buta Yarou series. A miniskirt-wearing Santa appears before Sakuta, calling herself Touko Kirishima and cheerfully informing him that she’s been handing out presents—Adolescence Syndrome. Apparently, one of the lucky winners is Sakuta’s classmate from middle school, Ikumi Akag