Koushaku Shisoku no Shuuchaku kara Nigeraresou ni Nai node, Nigenai Koto ni Shimashita

Fleur, the daughter of a baron, has been plagued by the advances of Victor, the son of a duke and a genius at magic, ever since he proposed to her as a child. So she tries to retaliate against him, which embarrasses her, but... it ends up making him happy, saying, "I'm so glad you think of me that much!"

(Source: Kadokawa, translated)