If she's that important to you, I'll throw you away

Lilith Norscott, the daughter of a viscount, is engaged to Sin Joad, the son of an earl and an apprentice knight. Sin, who is popular with many women for his sweet appearance, always prioritizes his childhood friend, the daughter of a baron, Mifon, and keeps telling Lilith to get along with Mifon. Mifon's fiance is Dil, the second son of the Margrave family and vice-captain of the Knights. Mifon is satisfied with Dil, who is foul-mouthed but good-looking, but he seduces Sin in an attempt to gain the upper hand over Lilith. Sin gives in to temptation, and Mifon toys with him, enjoying seeing Lilith in pain while denying that they are not that kind of relationship. Mifon, who desires the elation he feels every time he thinks he has defeated Lilith, finally crosses the line with Sin.