Liu Sha was thoroughly annoyed with how shameless these two are.
He managed to hack into Mo Aini's phone as well so he can now observe them as he did with Yang Caihong's phone. But now, he kind of regret doing it.
Of course they don't know they were being watched but god.... All the embarrassing things they did was disgusting even before the 'sausage' thing itself.
Liu Sha knows he was being petty and letting his emotions affect him, but he can't help it. He is jealous.
But he found himself more jealous with how much they loved one another rather than the fact that Mo Aini was with Hu Dongtian.
He was used to having A-Tian be chosen again and again over him. This wasn't even the first time he saw them being lovey-dovey or even having sex with each other. He had seen it all.
But something inside him has changed as well. Making him less callous and cunning, able to have no problem watching them as a system.