My Ex-Boyfriend Is Actually a Pure-Hearted Little Dragon!

Everyday Sweet Romance. The Female Lead Shouldn't Be Poor, and the Male Lead Should Be Filthy Rich

I'm looking for something calm and down-to-earth. I don't like stories where the female lead comes from an ordinary family while the male lead is a CEO, rich second-generation heir, or the richest man around. Either they're both rich or neither is. Not poor, exactly, just not wealthy, but comfortable.

If You Could Recommend Just One Book, Which Would It Be? I've Really Run Out of Things to Read