Oops! My Dumb Princess is a GeniusEpisode 4

Synopsis

In order to protect the embroidery shop left by her mother, she was forced to agree to marry her illegitimate daughter to the third prince, who was rumored to be mentally retarded. Three years ago, she fell in love with the new teacher in the mansion. She showed her love boldly regardless of worldly views, but her three years of love were met with his indifference and alienation, and even allowed the whole city to laugh at her for being shameless. Until by chance, she found out that he was actually the second prince of the dynasty, and he entered the mansion to teach under an assumed name because he loved her concubines sister, and her sincerity finally turned into a joke...