Wooyobitme's manga / #Black and White(521)

The uke and seme are both manwhores who have really high sexual libidos. The meet in high school and sometimes tag team and have threesomes with another girl, however both are "straight". The uke one day ends up getting fckd by seme and finds out he likes being a bottom. They become fck buddies. Later on uke finds out seme has loved him since they met. After some angsty stuff the officialy get together

This is Alpha x Alpha, they had an arranged marriage to strengthen their families. However they are having marriage problems because neither wants to be the uke. (Also in this world, anyone can get pregnant, even Alpha) they are under a lot of pressure to preduce a heir. The uke ends up going to sex therapy and finds out he likes things in his ass. However the seme ends up feeling betrayed that he went to therapy alone and had some other guy touch him (fingers only). This causes more problems however in the end both are willing to and want bottom (verse), they ended up having a baby