I read a manga on mangarock a while ago and I forgot what it was called. It is about a girl who gets warped into another world when she falls in a hole in a cave (I believe she was on a class field trip when she found the hole).
When she gets to the other world, she ends up liking the male mc (he has black hair). If I remember correctly, at first he thought she was a traitor/spy, but then he starts to love her.
Another detail I remember is a another female character who acts innocent in front of everyone and they all praise her, but she’s actually a bad person and she hates the female mc.
Please if you recognize this manga let me know!!!

It's been awhile since I read it, but what you're describing sounds kind of like this one:

Kanata Kara/From Far Away
https://www.mangaupdates.com/series.html?id=4875

Not sure if that's the one you're talking about, but it at least has a similar story.

To me it sounds a lot like Chuan Yue Xi Yuan 3000 Hou

I don't think it's Kanata Kara, it didn't have the cave & field trip part nor the spy or the girl acting all innocent while in truth being the opposite, but who knows, maybe that is the one you're looking for.

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