Honestly, if someone went through all of that to make me fall for them I'd think it was bit weird, but flattering. At the end of the day, the dad is happy and now so is Luo Yin. it's not exactly something to be freaking out over.
What he did is no different from pretending to like someone else to make someone else jealous. It happens all the time, you could say it's "manipulative" but at the end of the day does it really matter?
Gu Hai knew that as long as Luo Yin's father was single, he and Luo Yin would always depend on each other. By giving aunt her own shop and Luo yin's father a raise, they could afford to get married and have a happy life without being a burden to Luo yin because of money. It's not like his father was going to walk out on him, in fact his father did even give him the option to not let it happen. Luo Yin is the one who wanted his father happy and he could clearly see that being with aunt is what he wanted. Gu Hai just pretty much accelerated things.
He's manipulative, but I'll be damned if you guys think Luo Yin isn't
they both are which is why they are perfect for each other
allegedly it was a real life story based on the director's experience 
" queens who don't actually know what they want and play games better say anything 
