Because the Uke has morals?
he will still have a relationship after the Seme's divorce.
They can both wait.
If it is really true love, then the short time until the divorce is finalized is nothing.
Morals? He just gave the seme a blowjob in the last chapter! :p
My opinion: he said no probably because he's afraid of seme sudden commitment. The uke might felt it too good to be true and he might get hurt one day. Or maybe because he saw Taiga's mom before the seme drop the bomb??
Fuckbuddy is different than having a romantic affair.
Just like in Japan married men is fine going to Kyabakura, soaplands, etc. It's ambigous, but not adultery.
why the fuck not
You can finally be in a relationship
You were happy with him
Also why the fuck is the mom here