Aria offered a contract marriage.
To Grand Duke Valentine who was said to have sold his soul to the devil.
So she could protect herself and him.

[Marry me.]

Aria passed him a note that asks for his hand in marriage with her little maple leaf like hands.

[It's a contract marriage so we'll divorce 10 years later...]

The young master grabbed the note Aria was writing and ripped it to shreds.

"So where do I stamp it?"

"You told me you'll divorce me once we're older."

The young devil grew up and kissed her forehead.

"Since we have become adults, we have to instead make a contract for adults."