I really wanna see Yonghee's face once he finds out that they're living together. It'll be priceless
He asked how far they've gone, and got shut down. So he does know they are dating. I'm more concerned if he finds out they are living together with no other family, he'll be one of those friends that never takes a hint and leaves instead of constantly being there to hang out.
He found out they were dating in chapter 34. Yonghee comes off as really perceptive so I think he'll be able to take a hint (⌒▽⌒)
I bet season 3 will be them dealing with job hunting and rest of family. Although would love to see more of that best friend, cause he is one of most amazing characters ever.