DANRIM

‎Mokyeon receives a threesome proposal from Seonhwa, his friend and also sex partner. ‎The other participant is Nanjo, a man Seonhwa is currently seducing. He's rich and kind, making him a convenient companion, but the problem is that sex with him is incredibly boring. ‎Initially, Mokyeon's interest is merely casual curiosity, but during the act, he finds himself unable to take his eyes off Nanjo. ‎Sensing Nanjo's desire to be rescued from Seonhwa, Mokyeon makes him a discreet proposition: 'I want to possess your body, Nanjo. Can you open your legs for me?'

When Hwang Mok-yeon’s friend-with-benefits Chae Sunhwa proposes a threesome, he’s only mildly intrigued until he hears who the third is. Her target? Eun Nanjo: wealthy, polite, and perfectly presentable…but, according to Sunhwa, hopelessly boring in bed. At first, it’s just curiosity. But once the three of them are tangled in sheets, Mok-yeon finds he can’t take his eyes off Nanjo...not even for a moment. And when he realizes Nanjo may be more interested in saving Sunhwa than claiming him, Mok-yeon makes a quiet, dangerous offer. He leans in and says, “I want you. Do you think you could spread your legs for me?”

Chapter 26-30 of "Borderline" in English. Chapter 30 marks the end of Season 1.