I really was under the impression Woohyun when end up with Ha-eun. It really just felt shitty that a lot of the problems she went through got exacerbated by the distance Woohyun was putting between them throughout most of the story (Ina not helping with somewhat pressuring him too). I'm not saying they SHOULD have gotten together in the end because of that, but resolving their emotions and feeling for each other was a large chunk of the plot and why some of the issues occurred. The "let's just go back to being friends" really felt like a cop-out solution along with Woohyun constantly distancing himself from Ha-eun after learning what she went through when he wasn't around. It just didn't feel like those two ever got to be honest with each other and mend their relationship authentically because the story flash-forward 4 years and it's all worked out now. But I suppose the moment Chanwon was introduced, he would be Ha-eun's chance at a stable relationship (especially with what the ending teases.) But on the other and, I appreciate that the story does have Woohyun commit to Ina and go on happily marry her. I just don't feel like Ina, herself got flushed out because she comes across more as a foil to Ha-eun in the beginning and never seemed to make any effort to change their situation. I guess you could make the argument that Woohyun leaving Ha-eun left her with no one else but herself to face Daeho head on, making for a really intense and powerful moment for her growth. This is a happy ending above all else. To even think this much about the story elements proves how engaging I found "Sex Lessons"beyond just the sex scenes.