Haraiya Reijou Nicola no Komarigoto

After an untimely death, a Shinto exorcist finds herself reincarnated into another world as Miss Nicola von Weber. And that's just the start of her troubles. On Nicola's first day at a new school, she's reunited with her childhood friend Sieghart. He's now a handsome marquess who acts like a spoiled child around her, and wherever he goes, strange incidents follow. You see, Sieghart's beauty attracts both people and...otherworldly admirers. Nicola thus has to put her homework aside and use her skills as an exorcist to save him—all while trying to avoid his inevitable proposal, for Sieghart once swore he'd never marry anyone but her. And so Nicola's hectic, haunted life continues with a splash of romance, which she almost finds more annoying than the ghosts. All Nicola wants is normalcy, and this is the story of how she'll (try to) get it.

(Source: J-Novel Club)