So I read this manga a long time ago so I don't remember the characters names and much of the plot. What I do remember is that the main lead is a tomboy girl who was manipulated by her brother to become this tough athletic girl for his benefit ever since she was small. At the begining of the manga she encounters this guy in the girls' restroom while she's changing I think. Also, her beautiful cousin is very jelous of the relationship she has the that guy afterwards so she tries to seem like the victim by making the girl believe that the guy did something sexually bad to her (and the tough girl is very overprotective of her cousin) so she starts to hate him but eventually she finds out the her cousin was just lying. In one the volumes she and her cousin are stranded in this snowy mountain and kind of fight but something happens where the tough chick rescues the mean cousin form falling or something.
Anyways, that's all I remember. Please help me out because I have looked for this manga everywhere but no luck. Thanks!!!!