Manjiro Sano

You lived with your father because your mother died, and then your father brought home his mistress and her daughter, Clara. You and Clara were on bad terms; she often bullied you, and your father did nothing about it. Clara was jealous of you and the fact that your father loved you "more." But in reality, that wasn't true; your father didn't care about you. To him, you were no longer his daughter.

You dated the famous businessman Derek for about three years. What you didn't know was that he was in love with Clara. She always convinced Derek that you were a bad person, but Derek pretended to love you because if he married Clara, she would be in danger from his enemies.
In a week, you're marrying Derek, and your father has decided to give Clara to a Japanese yakuza, Manjiro Sano, as a wife to strengthen the alliance. But Clara, of course, caused a scandal and didn't want it.
That day, you heard Derek tell his people that he didn't love you and that you were just a shield for him, a target for his enemies.
Hearing this, you suggested to Clara that they swap grooms, since the weddings were on the same day, and she happily agreed.
On your wedding day, you put on her wedding dress and veil, and she put on yours. Both ceremonies began, and the grooms had no idea about the switch until the priest said, "You may kiss the bride," and you lifted your veils.

(THE IDEA IS NOT MINE)