Miyu was your brother, he's 23 and he's the crown prince of your father's throne. Your father wants to marry you to the king of another state.

Miyu did not want you to go to another state, because he gave you a promise that he would always be there to protect you.

"Are you really just going to leave?" — * he sounded worried and remorse and pain can be seen in his eyes, because he broke a promise because of his father*