Mantis (2025) Review

“Mantis” Netflix Poster

Director: Lee Tae-sung
Cast: Yim Si-wan, Park Gyu-Young, Jo Woo-Jin, Jeon Do-yeon, Sol Kyung-gu, Kim Tae-Han
Running Time: 113 min.

By Paul Bramhall 

When I first heard that streaming giant Netflix had greenlit a spin-off to its 2023 assassin flick Kill Boksoon, titled Mantis, I’d hoped it was going to focus on the newbie assassin played by Lee Yeon, whose killer action scene in the former gave her a scene stealing moment next to legendary actress Jeon Do-yeon. Not for the first time, I was wrong, and instead (as audiences smarter than me would probably have figured out) it focuses on an assassin who goes by the nickname of Mantis, briefly mentioned as being on vacation in the original. Moving away from the female assassin slant that Kill Boksoon continued the tradition of, for the spin off its Yim Si-wan (Unlocked, Emergency Declaration) who gets to headline as the titular character.

Mantis marks the directorial debut of Lee Tae-sung, who’s spent the last 20 years working in the directing department or as assistant director on numerous productions, including as assistant director on Kill Boksoon. Here he also tackles the script along with Kill Boksoon director Byun Sung-hyun, ensuring there’s a sense of continuity between the productions, and even allowing for some big-name cameos. We meet Si-wan as he’s tasked with offing a pair of assassins who’ve been going around performing unsanctioned hits, overseen by Sol Kyung-gu, making a cameo appearance as the chairman of the hitman organisation that governs the assassin business. While on a break after completing the hits, Si-wan learns that Kyung-gu has been assassinated himself (in the final scene of Kill Boksoon), and with his death the assassin job market has been thrown into turmoil.

From there it becomes increasingly difficult to ascertain what exactly Mantis is about. Si-wan has always harboured a crush on a fellow assassin played by Park Gyu-young (LOVE+SLING, Wretches), with the pair having grew up together as orphans. But is Mantis their love story? Not really. The pairs mentor, played by Jo Woo-jin (The Match, Harbin), has come out of retirement and plans to rebuild the hitman organisation that Kyung-gu oversaw, hoping to bring Si-wan back as part of it. But is Mantis a tale of hitman corporate greed? Not really. There’s a villainous software CEO who wields both power and money, believing he can create a new organisation of assassins, one which doesn’t need to adhere to the strict code of conduct Kyung-gu’s outfit insisted on following. But is Mantis the tale of a villainous CEO looking to start a new world order of assassins? Not really.

Instead, for almost 2 hours the plot threads intermittently overlap with each other, but at no point do any of them become developed enough to actually care about their outcome. Si-wan may be able to look the part in a publicity still, with his weapons of choice being a pair of handheld retractable scimitars (which when held with the blade facing downwards, give the appearance of a mantis), however onscreen he never really convinces as a deadly assassin. This is exasperated by the fact that, for most of the first half, the tone is closer to a light-hearted comedy or a teenage drama, with Si-wan’s attempts to build his own organisation (consisting of fellow assassins Gyu-young, and K-drama regulars Bae Gang-hee and Hwang Sung-bin) feeling like we’re watching a tale of youthful vigour overcoming the tribulations of the world.

If there’s one recurring theme that may be responsible for how Mantis got green lit in the first place, it’s that of jealousy. When Si-wan and Gyu-young were training to make their debut in Kyung-gu’s organisation (drawing parallels to the world of K-pop, which I’d like to hope was an intentional choice), Gyu-young was told she could never be as good as Si-wan, a choice of words which has stuck with her through the years, and gradually sets them on different paths as the plot progresses. Similarly when Woo-jin was working closely with Kyung-gu, a confrontation between the pair saw him receive similar feedback, with the latter’s death now giving him a chance for retribution. Ultimately all of them want to be perceived as the best at what they do, with the decisions they make done so in the belief that they’ll become closer to achieving their goal.

Other themes flit in and out as haphazardly as the various plot threads. Tae-sung seems to want to say something about the struggle of Korea’s youth in finding employment, with the ability of Woo-jin’s organisation to bankrupt its smaller competitors feeling like a cynical swipe at Korea’s chaebol conglomerates. However its handled clunkily, and is never developed to a point where it resonates in a meaningful way. The same could be said across the board, with this example actually being one of the lesser issues. The biggest one is arguably the relationship between Si-wan and Gyu-young, with the formers unrequited love for the latter providing the perfect scenario for a quietly simmering tension to develop between the pair once the secret is out, but alas it’s not to be.

Whether it be down to the script, performances, or both, the pair have zero chemistry, and as a result what should be a significant revelation lands with a meaningless thud. Si-wan’s performance certainly isn’t helped by the fact that, compared to the internal conflicts Gyu-young’s character has to wrestle with, the character of Mantis comes across as woefully underwritten. For a movie to give its name to the least interesting character is a serious misstep, and despite me starting this review by saying Tae-sung’s debut moves away from the female perspective of Kill Boksoon, it’s ultimately Gyu-young’s character that will keep the audience watching.

The one area where Mantis is superior to Kill Boksoon is in the action department, with action director duties going to Ryu Seong-cheol, a veteran of the industry who’s work can be seen in the likes of Alienoid and Uprising (and clocks in a rare front of the camera role in 2008’s Spare). The option to go with blades instead of guns allows for a certain Hong Kong flavour to come through when the fights do hit, and for kung-fu cinema fans there’ll be echoes of Tong Gaai’s Shaw Brothers work when Woo-jin breaks out his weapon of choice – a pair of modified tonfas. The editing sometimes works again the rhythm of the action, and there’s a few moments of awkward wirework usage, however for the most part the choreography leans into a level of intricacy not usually found in a Korean production.

Falling firmly into the category of kung-fu cinema fan myself, part of me desperately wants to say the action makes Mantis worth clocking in a watch, however the unavoidable fact is that it never feels like anything significant is at stake when the fights do break out. Without any kind of emotional investment to care who wins or loses, when the action does come it simply feels like a hollow spectacle, admirable for the performances and technical expertise on display, but completely devoid of any engagement within their context to the plot.

Likely due to Kill Boksoon director Byun Sung-hyun contributing to the script, my assumption is he was able to convince Jeon Do-yeon to make a brief cameo, turning up for a couple of minutes to give Si-wan some relationship advice, marking one of the more embarrassing moments in her filmography. By the time Mantis crawls to its final reel though I got the distinct feeling embarrassment had sunk in even for Si-wan, who wraps things up by delivering a line directly to camera that’s spoken so half-heartedly, you have to wonder how they didn’t go for a 2^nd take. Netflix has a pretty shoddy track record when it comes to Korean sequels, and while Mantis doesn’t quite reach the dire depths of Believer 2, its dangerously close.

By Paul Bramhall’s Rating: 3/10