It's from manga raws. Ml loves the crown prince's fiancee. It's just that mc and ml kinda missed each other. When ml knew for sure that he loves fl and not princess [when he saw his ex-crush at a ball] that's when fl [she was already having doubts about ml not loving her the way she does cause she kinda told ml she loves him but he said "I like you" <y'know how japanese have different ways of Iloveyou> and then she noticed how he acts different when talking about crown princess] then at the ball she saw how he looked at the princess and realized he has feelings for her, she was about to ask him but he knows mc saw him and he basically ran away. Then MC's ex went to talk to her for a bit said sorry then wished for her to be happy but then mc was like [happy? Why now when I now know my husband yearns for someone else] then ml came back. After that when they were going home that's when she decided to stop loving him and just stay as "partners".
Tldr: she said she loves him -> he said "I like you,not love". -> Ml saw ex crush ->mc discovered about said crush -> Ml then admits to himself he love mc -> but then Mc decided to stay as contract marriage partners
the ml also have someone else he loved wtf. I hope it's not gonna end up like the title. My heart hurts for fl uuughhhhh why read it past me!!