Nononono by Okamoto Rin

Summary from Mangatraders:
Nonomiya Yuuta, a Skii Jumper aiming for Olympic Gold, bursts onto stage with his exceptional skills. However, his biggest problem is that he is not really a "HE"... This Yuuta is actually Nonomiya Yuuta's twin sister, Nonomiya Nono... And with Women's Skii Jump not being an Olympic catagory, hiding her true identity is the only way for her to achieve the dreams of her father and brother.
Add in 2 psychotic upperclassmen in the ski jump club who may be planning to commit, or already have committed, murder, and you have an explosive mix.

Contains scenes of attempted rape and occasional extreme violence and cruelty. For mature readers only.
I recently started with this Manga and I haven't been able to stop reading it.
It's definetly worth giving a try. (Even if you're not into winter sports)