I think the plot was that she was recovering from a traumatic event (possibly rape) and it may have involved her brother and some fluffy incest, though I'm not certain. I just remember loving the main girl (Mayu's) design- I used her as my avatar a lot a few years back, but now I can't remember the manga's name!

Here's some images I still have, if it helps.

[url]https://imgur.com/a/RGFEIgA[/url]

it's Gotsugou Soukan