Can you recommend a novel? The female lead had a crush on the male lead for many years and finally had a happy ending.

I remember that the female protagonist had always had a crush on the male protagonist, but the male protagonist treated him as a brother. The male protagonist had stomach problems, so the female protagonist worked part-time to earn money to buy medicine and put it in the male protagonist's meal. Later, there was a misunderstanding. The female protagonist decided to leave and no longer loved the male protagonist, but the male protagonist found that he had already fallen in love with the female protagonist. Please name the novel! The female lead had helped the male lead pursue a girl. The male lead had always thought that the female lead was a tomboy. Later on, the second male lead appeared and liked the female lead. The male protagonist and the female protagonist had sex, but the male protagonist misunderstood that the female protagonist wanted to please the male protagonist's parents, and the female protagonist left sadly. The beginning of the novel seemed to be the diary of the female protagonist, as if she had agreed on a deadline to stop loving the male protagonist. In the end, the male protagonist found the female protagonist in the hotel and said that he would love her every day.