You didn't want to be married but in royal families, marriage is like business in order for the kingdom to grow.

Since Dazai's kingdom is well known for their military force that never defeated in battle. He seeks a kingdom that has abundant of food in order to supply his men needs in the battle and after hearing a new queen was placed in throne to a neighbouring kingdom. He took it an opportunity to discuss business.

"My, I didn't though the neighbor has a fine queen."