I'm guessing this is going to be a long shot, but are there any fake dating/marriage series that stay platonic? Bonus points if they are mutually consenting to using each other for their own means. I'll accept it if one of them eventually falls for the other, but they don't end up together. Even better if they find their own love or happiness elsewhere.

Uh, I will say that I don't really care for Watashi wa kabe ni naritai, but I will be more than happy for suggestions like it that are better executed. I can't believe my investment in a premise that I was 100% interested in, and even excited for, was killed within two chapters.

Everything Was a Mistake: it's not the main plot focus, but the female lead is in a mutually-fake engagement with her platonic male friend, who's secretly in love with FL's best female friend. The actual romantic male lead is FL's jerk childhood friend. FL and platonic fiancé don't hook up, but warning that the romance plot threads drag on frustratingly otherwise.

Suteki na Kareshi: also not the main focus, but at one point the FL has a mutual fake-dating plan with a guy for about a volume or so. They don't stay together.

Ngl, a villainess reincarnation with actual platonic male friends, and there's no chance of a love triangle is already enough to draw me in. I thought I was done with villainess reincarnation, but I'll give this a shot.

Suteki looks like it would be a good time. It's from the author of OreMono, so that's also a good sign. 4 volumes out of 14, last update 2 months ago though... Whelp, I've waited for longer.

Thanks for the recs!

Oh, this is a good request. I'll be wracking my brains for any series that fits this for a while, I suspect.

Anyway, for now, this doesn't exactly fit, but Now That I've Been Chosen to Be the Villainess, I'll Show You an Elegant Performance! has the main character get into a pretend relationship with the crown prince in a convoluted attempt to matchmake him with someone else. She has no feelings at all for the crown prince, and the male lead seems to be someone else, if I'm reading the romance cues correctly. (Note: the crown prince is not informed that the relationship is pretend, though he also shows no signs of romantic feelings for the MC either.) The whole series has so far been a pretty funny, yet loving parody of the whole villainess subgenre, actually.

The only one I can think of at the top of my head is Scum's Wish. The fake relationship is part of the main focus of the story. The manga description covers it pretty well if you want to check it out.

Conclusion of relationship if you don't care for spoilers:

They don't end up with each other.