From Yen On:
Alisa Mikhailovna Kujou is Seiren Private Academy’s “solitary princess.” She’s a half-Russian beauty with silver hair, at the top of her class a student council accountant, and completely unapproachable. For some reason, she’s also taken on the responsibility of reprimanding the slacker who sits next to her in class. Masachika Kuze is constantly frustrating her by falling asleep, forgetting his textbooks, and just being an overall unexemplary student. Or at least, that’s how it looks from the outside. She may put on a tough act but she doesn’t mind Masachika as much as others would think.
She even lets him call her by her nickname Alya. Anyone hearing the comments she mutters in Russian under her breath might know how she feels, but since none of her classmates understand the language, she’s free to say whatever she likes. Except there is one person who knows what she’s saying. Masachika eavesdrops on her embarrassing revelations, pretending to be clueless all the while wondering what her flirtatious comments mean.