Both stories are centered around body swaps that happen out of envy/unhappiness about the ML's/FL's current lives.

- ML tries to change his fate by using a supernatural opportunity that he has to keep secret from his social circle
- items that enable this opportunity have limited uses
- identity swap/time travel introduce new challenges and affect relations with ML's loved ones (family/partners)
- crime/murder mystery elements

Fan of one may likely enjoy the other.

- both shows like to switch between past and present to gradually reveal the events that led to the current situation and to uncover the mysteries related to it (the use of sepia/yellow filter is also similar)
- there is a lot of injustice happening around the main characters and it's very difficult if not impossible to deal with it
- both shows are consistently dark throughout all of their episodes

I'm pretty confident a fan of one will like the other.

- both shows like to switch between past and present to gradually reveal the events that led to the current situation and to uncover the mysteries related to it (the use of sepia/yellow filter is also similar)
- the past is full of dark events; Nine is a time travel show so it also lets us experience how life of some characters can change if those events play out a little different

King of Pigs is consistently heavy from the start until the end, Nine takes like 1-2 episodes to start showing its true colors and the further it goes, the better it gets.