So i remember only bits of the plot but the mc has a system and in this arc he has an indifferent uncle(the ml) think? And then the mc request for the system to give him a little mini me that can only be seen by the ml. The little mini me shows his thoughts which contradict his actions for example: Mc acting very angry, the mini me is dancing happily.
Not sure if this is it but this novel isn't a QT My Outside Expression Is Different From My Inner Expression
If there's not another QT with the same arc, then I'm pretty sure, @stellar_soul is correct. Because I've read the first half of that arc as well. MC's setting is an arrogant and overbearing little 2nd generation-ish boy who's in love with an actress. She in turn has a blind date with ML, who is MC's uncle and is being constantly harrassed by the original in all kinds of ways. But as far as I recall not blood related. (Don't take the last sentence for granted). MC uses his system to get this little phantom on his shoulder which only ML can see and ML, who was already quite unhappy with the original, finds out that MC is in fact nothing else than a tsundere. While MC is following the setting by making a fuss and trouble at every turn, the little guy on his shoulder is selling meng like no tomorrow. As I said, I didn't read the whole arc, so I don't know how exactly MC managed to get bedded by ML, you'll have to read it for yourself.
CatNap should be right. Bit instead of the MC asking for the Golden finger, It attaches to the ML instead.
If it's with an uncle, then stellar_soul is correct! 'Everyone Knows I'm a Good Person' arc 9, Uncle Love Me Again. MC tms into spoiled rich boy and uses the mini me skill to help decrease the ml uncle's animosity level.