Mantis Yim Si-wan as Lee Han-ul in Mantis. Cr. Cho Wonjin/Netflix © 2025

From Kill Boksoon creator Byun Sung-hyun & writer/director Lee Tae-sung, Mantis is the much-anticipated spinoff from the South Korean assassin thriller Kill Boksoon that was a surprise critical hit for Netflix back in 2023, garnering a “Fresh” rating (79%) on Rotten Tomatoes. The film has also racked up almost 28 million views since its release making it one of the most successful South Korean Netflix Original Films to date.

Kill Boksoon led its audience into an assassin underworld led by the largest & most prestigious organization, M.K. Ent, and their leader, Cha Min-kyu (Sul Kyung-gu). During the events of the original film, Cha Min-kyu & his chairman sister, Cha Min-hee, were taken out by their best assassin, Gil Bok-soon (Jeon Do-yeon), leaving the organization in disarray with a possibility of complete destruction.

On a script co-written by Kill Boksoon’s Byun Sung-hyun & Lee Tae-sung, Mantis rejoins this universe in the immediate aftermath of MK’s downfall; a new world where the rules of conduct for the secret society of contract killers have been cast aside and the splintering of former companies & alliances has destroyed the structure that kept this world in check. No one knows who will emerge to fill the power that MK held over the industry or if MK will still exist under new leadership.

Enter: Mantis (Squid Game standout Yim Si-wan). A young, highly skilled, but incredibly pompous MK agent and former colleague of Gil Bok-soon, who returns from vacation to the newly collapsed order of the hired killer industry. Upon learning of what has transpired, he seeks to create a new company with his fellow trainee Jae-yi (Fellow Squid Game star Park Gyu-young) while seeking the counsel and potential shows from his mentor Dok-go (Narco-Saints star Jo Woo-jin), who has come out of retirement to reclaim MK after being forced to retire from the company years ago.

With so much uncertainty and a power vacuum created after the heads of MK Ent were taken down, Mantis, Jae-yi, & Dok-go all seem to have something to prove as they attempt to take over the top spot in the contract killer game.

The beauty of Kill Boksoon was that it’s a focused story about one elite assassin’s crisis of conscience as a contract killer with strict rules & mandatory assignments who is learning to be more true to herself from her relationship with her daughter. The film builds up Boksoon’s complex relationships with her longtime boss & her daughter until she is forced to choose between them by the story’s end.

Unfortunately, while picking up immediately after the actions of Boksoon, Mantis does not share the same focus and character building that made the original succeed. This spin-off takes arguably the least compelling aspects of Boksoon, the rules/punishment/power structure of the assassin world, and makes it the backbone of their story. In the original, those elements were a value add to the mystique of MK and created the structure for the complex situation Boksoon and her boss find themselves in following her refusal to fake the suicide of a young college kid. In Mantis, those elements seem to add more dialogue about work distribution & unemployment among killers than they do to building the film’s three main characters to a fever pitch for industry domination.

As for the film’s characters, Mantis already seemed an odd choice for the spin-off’s protagonist from its outset given that he was only mentioned as “on vacation” in the first film without any additional detail of his abilities or stature in the MK rankings, but with his name on the marquee and Boksoon taking a backseat, you would figure he would be the young heir apparent that would take the mantle as the “best knife” in the business. But the film feels more content with making him a strong fighter with a soft spot for his MK training school rival Jae-yi, turning his brash, flashy upstart beginnings quickly into mush.

Picture: Netflix

While his motives are noble and sweet, Mantis seems to have no motivation other than that of satisfying Jae-yi’s needs. Even the film’s conclusion leaves you wondering if all of his actions & sacrifices put him in a better place than where he started. Jae-yi has something clear to prove in the film and feels very akin to the story of Dok-go. I would almost rather see a movie about her as the lead, climbing her way back after being let go by MK, and then trying to take it back when they are at their most desperate. The “will they, won’t they” of Mantis & Jae-yi doesn’t work much at all. The movie hinges on its success and suffers for it.

If you are a fan of Kill Boksoon, as I completely am, you probably came to this film hoping for a new assassin with a killer story to take up the power that Boksoon destroyed in her wake, complete with the same incredible blade action and balletic movements. While the action can be comparable at times, the story does not compare. Instead, we see a dizzying, poorly paced story about status, broken allegiances, & the challenges of relationships in a violent industry, with a central character that takes a backseat for over half the sub 2-hour runtime. Jae-yi may not want his pity, but we also shouldn’t be put in a position to pity him either. In the one job of justifying a universe-expanding spin-off character movie, the Boksoon Cinematic Universe did not rise to the challenge. Wait for the battle highlights on Netflix’s YouTube page.

Watch Mantis If You Liked

• Kill Boksoon
• John Wick
• Squid Game
• Ballerina (Netflix-South Korea)
• Carter

MVP of Mantis

Action Directors Seo ji-oh Lee & Seong-Cheol Ryu

Even though the story, pacing, & characters don’t measure up to Kill Boksoon, it doesn’t mean we can’t have a good time with weapons!

Longtime stunt performer turned director/choreographer Seo ji-oh Lee (Uprising, #Alive) & newcomer Seong-Cheol Ryu brought inventiveness, creative staging, & the signature agility and athleticism of the franchise to every scene they directed. 3 way fights, nasty kills with missing limbs, Mantis’ sickles! This is why we love these movies.

Don’t expect the quality writing, themes, & motivations of Kill Boksoon, but at less than 2 hours and similarly solid fight choreography, South Korean action fans (and “Squid Game” fans I suppose) may find something to like in Mantis.