So I'm looking for a romance that goes something like this:

Basically there's a cheerful female lead who meets some cool guy who is pretty cold to others or whatever and ultimately she realises he's got a really painful past or something.
And for a long time the story focuses on how she tries to get close to him and help him heal his pain or what have you.

And for at least a few volumes, the cheerful female seems like she has no worries of her own outside of her new concern for him and everybody else assumes so too...

Until out of nowhere it suddenly comes to light that her life isn't as perfect and happy as it seemed. And now it's the guy's turn to care for her. (The more unexpected this sudden twist, the better!)

And it has to be something non-cliche, not just her mother isn't around anymore or something. Something dramatic like somebody kidnapped her and locked her in a room for weeks or something and she's never really got over it.

Anyways, when thinking I wanted to read something like this, I couldn't decide whether I'd find that actually this is a really popular plot, or unfortunately it's actually really rare.

We'll see, thanks guys!

Side note: Please nothing with a horrible tragic ending.

Sounds like Mars. Sorta.

Thanks for the recommendation. According to my complete list I've already read it, but I can't remember it at all so it's as good as getting a new manga
On the page it also says there is a live-action drama. Not sure whether I rate drama adaptations but could be worth a go...