Becoming a princess once was supposed to be a great honor, but then she was betrothed to a stupid prince. As everyone knows, the ninth son who is the most favored by the Holy Emperor was once heroic and invincible, but was tortured into an idiot by an accident. How should we deal with this huge "happy event"? But she didn't want to be the wife and nanny of the Ninth Prince, so she had a lot of followers around her. But what's going on with the music every night? Isn't the idiot prince stupid? And there are also suspicious people around her. It turns out that she is not the daughter of a merchant, but a princess of another country. This is a tender story between a country's beloved princess and a country's cold prince.