Looking for one sided fake dating where the FMC is under the impression it's 100% real?

Okay, I tried searching for this but couldn't quite find what I'm looking for.

I'm wanting to read something where the MMC enters into a relationship with the FMC (could be a bet but also personal gain, revenge, curiosity, hell maybe he's a reporter trying to learn her dirty secrets idc) but the FMC totally thinks it's real. Most of the recs I've seen both parties enter into the relationship knowing it's fake. It has to be real on the part of the FMC. Maybe she's a little thrown off but everything being fake is not on her radar.

As the plot progresses the MMC starts to realize he has actual feelings for her, knows he needs to come clean, but his motives are revealed before he can do so

I'm really looking for that gut punch when the FMC finds out the MMC started the relationship for nefarious purposes and cuts him off. Some heavy duty groveling is ideal, but I'll take what I can get.

I don't know why but the only thing I can think of that comes remotely close is Disney's Mulan where Shang is devastated when he finds out his BFF Ping is a girl lmao. And then she has to save a freaking country to win him back. This is kind of the vibe I'm looking for lol.

Anyone have anything like this?

Any genre, no triggers.