I Accidentally Seduced the Male Lead’s Younger Brother

"No, I don't want to." I flatly rejected my ex-boyfriend's proposal to have an affair with him. "The Young Master is not my taste. If I must say, your younger brother is much preferable." "What? You prefer my younger brother?" Yeah. Not you, but your brother. *** That younger brother' came back to me as a beast with a decadent beauty. "I've never forgotten you for a moment. Please marry me, noona." On top of that, he's even holding the engagement document that I signed as a joke during childhood. No, weren't we only playing house? "Could it be that your tastes changed while I was away?" Lexion's eyes were full of life as he asked. It was as if he would kill someone right away if he were to find out they were my type.