Bai Yueguang Only Has Three Months to Live. Let Me Accompany Her to Death.

Also known as "The Promise Under the Cherry Blossoms", (unhappy novel, no time travel, no rebirth, no system, no invincibility), campus + sadomasochism + single female protagonist + academic dominion Lin Dandan is a top student with both good character and academics. After meeting Xu Yaxin, the two agreed to be together for the rest of their lives. Unexpectedly, Xu Yaxin was terminally ill and only had three months to live...