Lucas is enviously ML based on possinle and presentable analyzations and cliche.
Since most Isekai always show the ML first. Also, even if the FL says she will not fall for him, she will, that's exactly what she plans but always the author will ruin that plan of hers and make her fall for him.
And I do analyze that the true ML is Lucas, no matter what handsome men appear, it's always the hero. I have read another story for which the FL reincarnated 5 times and the childhood friend of hers is a hero, both sweared to get married but the hero marries the princess. But there was actually a reason why he chose to marry the princess and not the FL, it's so warped and emotional at the same time, you feel angry towards the hero but soon regret that you hate him for leaving her. The her in her past lives will be reunited with the heroes and she will get the freedom to love and marry her childhood friend hero. So I really do wanna know if that plot will be the same as this but there is also a possible plot.
Like how she says it's a game she's in, what if the maker of the game eventually think if no progress and spice in the story if the childhood friend is involved, so he then chose to make the princess his wife.
ACTUALLY I HAVE A LOT OF POSSIBLE PLOTS OF WHERE THIS STORY GOES AND I'M TOO NOT STRAIGHTFORWARD. BUT ALL I KNOW IS THAT FIRMLY THAT LUCAS IS ML EITHER WE LIKE IT OR NOT
I found the manga! https://www.mangago.zone/read-manga/this_time_i_will_definitely_be_happy/
And yea that one has a happy ending and I liked it, if you want to continue its story you will need to read the novel and the novel is translated
That's the problem, I don't have a lot of information to provide, because when I started reading it, there were only like 5 chapters, and it was few years ago.
Still the story is rly similar to manga u mentioned, hero went to defeat demon king, she waited, but when she went to capital to see him, he was already a fiance to Princess, and it happened few times, couse her life is like restarting, or something, after few heartbreaks she prepared herself, and tried to start her life in new place, she decided to forget about hero, and live her life happy this time.
So as you see it's almost identical plot, the only major difference is that she isn't reincarnated, but she is re living her life.
BTW I finished the manga u mentioned, it was quite nice, perfect number of chapters to binge it :)
I like those kind of stories, ther is no major drama or love triangles, if u also like this kind of stories i recommend Mahoutsukai no Konyakusha, and The Villiainess Is Adored by the Crown Prince of the Neighboring Kingdom.
If u know more stories like this I hope u will share them with me :P
I tried to think of one, but I still can't because not much details
But here's the one I mentioned before. Probably not the one you mentioned since she reincarnated each life.
https://www.mangago.zone/read-manga/the_prince_was_my_lover_who_threw_me_away_in_my_previous_life/
It's sad to know that Arnold is not the ML, welp we gotta accept what the author gave us.