It's so good I highly recommend experiencing it for yourself
https://www.novelupdates.com/series/mochiron-isharyoseikyu-itashimasu/?pg=4
(if you don't want to I can tell you tho)
Yeah please tell me I just want a fast but clear spoil
So there is a photo taken of the main couple. However, the FL realizes it so she organises an event where if someone spends a certain amount or more in her shop, they will get to take a photo with the prince, the FL's brother and the other guy. So when the ex-fiance tried to use the photo to descredit her, everyone was saying "wasn't that the promotional event photo?"
Continued spoilers
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So then even when the fiancee and the "heroine" use that as a defense it has little impact. Basically, the showdown happens at the school dance. The king is present. The FL's father delays the fiancee's father long enough for the two lovers to announce that the engagement will be broken and then he and Julie will be engaged. As said above, they claim she cheated on him with the prince. Then we have a good "HOHOHO" evil laugh session while she gets out all of her evidence against them. The engagement is broken and reformed with Julie as the partner just in time for the marquis to arrive. He basically faints and tries to undo everything when he realizes what his stupid son has done. But because the King is there it goes according to plan.
As condemnation scenes goes, it has few surprises, but it's so satisfying to read.
Thank uu love uu
Spoil me pleeaaasee is the next chapter will be a cliché with the plot that Yulia and the Prince having an affair ? Before the story was very original until now uwu