I read the still cuts and character introductions of 21st Century Grand Prince's Wife.

You play Prince Ian. It's said that he lived in seclusion, facing the limitations inherent in being the second son of the royal family and the only younger brother of the former king. Despite this, the people regard him as "the most beloved royal in the Republic of Korea," and they give him absolute support for his handsome appearance, exuding dignity, and charisma. After the deaths of his father and older brother, he suddenly ascended to the throne as regent for his nephew, but he's constantly under pressure.

In the midst of this, Seong Hee-joo (IU), a commoner turned chaebol, receives a contract marriage proposal from Robotu...

I think he also accepts the offer to increase his own power.

After reading the role, I'm even more excited.