Suenagaku Yoroshiku Onegaishimasu

After her father has suddenly passed away, Takatsukasa Hikaru was adopted by her cousin, Kuzukiri Kiyomizu. Hikaru expresses that she is madly in love with Kiyomizu, but he is having none of it.

(Source: Comikey)

Note: Chapter count includes one additional Special Episode epilogue chapter.