Do Kyungsoo is moving in the city because he's getting married In three days. Yes he's getting married at the age of 19 with the consent of the parents its legal to get married at that age (23 is the marrying age without a parents consent). It was an arranged marriage he never expect that still exist. His grandfather served in the royal army for 48 years and was one of the trusted men of the King Jonghyun. He died while protecting the Crown Prince Jongsuk and as a gratitude the King promised to marry off the first born of the Crown Prince to his daughter's first born. The only problem that the King didn't anticipated was the first borns could be both boys. The King must be a man of his words and when Crown Prince Jongsuk son turned 16 they will get marry under one condition it must be a SECRET it is to protect the royal family and to avoid the scandal but the Royal Secretary forgot to mention to him that the elders came up with a plan on how to keep it a secret by dressing him up as a girl.