He needs therapy. Like, not dick, not a good boyfriend. He needs therapy! He doesn't have an exhibitionists' kink, he isn't just ok with one night stands or whatever. His lack of self control means that he really was traumatized by what his brother and his brother's ex did to him. And now he's gonna hurt his boyfriend because no one ever caught on that he has deep seated issues and dragged his ass to therapy.
Like if Baek would calm the fuck down for a second he could attract Seo,
But that wouldn't be funny tho lol