Chuusei Kokoro ga Nai to Iwaretanode Konyaku o Kaishou shite Agemashita.

https://www.cmoa.jp/title/309327/

One day, while strolling through town with her fiancé, Rubina—the daughter of a viscount—gets left behind when he becomes completely absorbed in a conversation with another woman. Confused and unsure what to do, Rubina is approached by a mysterious gentleman named...