Kill Bok Soon

Also a very nice Thriller movie, with lots of action scenes. Has a interesting mentor mentee relationship plot as well.

A teen in both is being raised by a killer/group of killers. It affects their relationship. In Kill Bok Soon a teen doesn't know about them being a killer, In Hwayi: A monster Boy a teen knows and is being raised to be a killer too.

These films offer a blend of thrilling narratives, complex characters, and intense action sequences that should appeal to fans of "Mantis."
Also, they are from same universe!

Working woman single mom trying to save her son fight against crazy evil villain. Intense, danger, one against group.

Assassin's/killer theme, both action packed would recommend if you've watched either or.

both have badass female leads with an ulterior motives and a backstory behind their doings. jiwoo was revenge driven in my name who wanted to avenge her fathers death. after a series of events she gets to know that the person she joined hands with is the real killer and that aggravates her thirst of killing. i feel like the protagonist of this drama also has a similar story.

Both movies have a FL with a "particular set of skills" that make them dangerous & useful.............................................

Both are a kmovie about a female killer, the two worked in a violent job and ended up killing everybody. Kill BokSoon has a more complex storyline with other characters, while ballerina has an emotional thing on it.