Honestly, all the posturing can be for show considering the events of ch 153 when SHJ voiced out genuine concern about HYJ. He obviously sees HYJ in a different light from everybody else, regardless if that implication is romantic or not for providing amusement in this life that seems to be stagnant and repeating for him. Id say the posturing can also come from him wanting HYJ to improve upon himself because SHJ obviously sees so much potential about him.
I think there’s something underlyingly romantic about that when thinking of SHJ playing the bad guy role so that Yujin betters hinself in this new life he found himself in

I think SHJ did all this posturing just so he can see HYJ all dressed up and polished for him. He kinda liked what he saw during his birthday and he wanted a second version on his terms. (づ ̄ ³ ̄)づ