Oh hey I remembered something actually!! About the second couple they are not going out because of a dare but because the uke tells some girls that the seme is his boyfriend to protect him or something! Sorry it's all jumbled in my head (￣∇￣")
Could it possibly be this one?
http://www.mangago.zone/read-manga/owaranai_fukou_ni_tsuite_no_hanashi/
Yesssss!!!!!!! This is it!!!!!! Thank you so much!!!!!! I have been looking for this manga for so long!!! Thank you!!!!!! ヾ(☆▽☆)
I don't remember it very well, but it was high school setting. So I think it was two couples, I liked the second better. For the first couple I think the seme was out of high school and at their meet up, he meets his school crush and after a few drinks end up molesting him in a car, or something like that. And about the second couple the uke was a kind of sleeping with a lot of girls and the seme dares him to sleep with him or something. I know it's very vague but I read it a long time ago. Any help would be greatly appreciated. (๑•ㅂ•)و✧