I don't think it is. Let me explain why:
- Majority of josei are romance manga, which is not the case here
- You could argue that this is one of those rare non-romance-focused josei, but there's a strong male-gaze aspect, which I suspected from the start and the more recent chapters confirm it. The dress and boots combination that she starts wearing from chapter 7 onwards is a male idea of what looks good and there are unnecessary zoom-ins on her boobs
- Aside from the male gaze aspect, the art itself is very much what you would see on a Seinen instead of Josei. This might go unnoticed if you're not familiar with the differences, but josei usually is more cutesy while this one resembles Lookism
- Seems like at least one of the authors is a man judging from his name (Kwak Dongju) and men do not usually write josei                                            
                                                I get where you’re coming from, but I’d argue that this manhwa actually fits better under Josei than Seinen. Here’s why:
1) Not all Josei = romance.
Romance is common in Josei, but it’s not the definition. Josei is really about stories that resonate with adult women, whether that’s romance, work-life, or darker psychological themes. This series deals with power dynamics, self-worth, and manipulation and those are issues that adult women relate to even without a love story.
2) The “male gaze” doesn’t disqualify it.
Plenty of Josei titles (Midnight Secretary, Paradise Kiss) include sexuality, stylish outfits, and even provocative framing. What matters is the narrative perspective. Here, the female lead is still the one driving the story. She has agency, and the focus stays on her choices and struggles.
3) Art style ≠ demographic.
Josei isn’t always “cute.” Some of the most iconic Josei (Nana, Tramps Like Us) have gritty or stylish art that could easily be mistaken for Seinen. What really matters is the intended audience and the emotional themes.
4) Author gender doesn’t decide demographic.
Sure, men don’t usually write Josei, but it’s not unheard of. Demographics are based on audience and themes, not the author’s gender. There are plenty of male authors in Shoujo/Josei spaces, and their works are still classified that way because of content.
5) Seinen usually leans into external conflict (action, crime, sci-fi), while Josei digs into internal and interpersonal struggles. This manhwa is clearly more about psychological survival and self-value than about action or politics. That puts it much closer to Josei in my opinion! Just a darker, non-romantic version of it which deviates from the norm but still is in the genre.                                            
                                                I think you’re basing your argument on some really limiting assumptions. Like Josei has to have a “cute” art style, or only be created by women. That’s not how it actually works. Josei simply means stories aimed at adult women, and those stories can range from romance to workplace drama to darker psychological themes.
   This series fits that perfectly: it centers on a female lead, deals with power dynamics and self-worth, and focuses on internal/emotional conflict over external action. Those are classic Josei traits, even if the art style is more "seinen" than "josei" or the authors aren’t women.
   So while it might borrow some visual elements you’d expect from Seinen, at its core the perspective and themes align much more with Josei. Assuming it can’t be Josei because it doesn’t fit a narrow checklist really misses the broader picture of what the genre represents.                                            
                                                I said it myself that not all josei is about romance, not all josei has cute art style, but I'm looking at these aspects together. It all adds up to this title not being josei.
Also, I don't deny that there's sexual frames in josei manga, but there's a difference between female gaze and male gaze. For instance, there's lots of webtoons that are just porn, and yet there's a clear difference between porn aimed at women and porn aimed at men and you usually can tell with just one glance. The outfits, the angles and the art style play a part in this, we can't pretend it doesn't.
And of course the gender of the author doesn't dictate the genre of the comic, but how many men write josei or shoujo? It's far more common to see women writing seinen or shounen than men writing comics with female demographics.
And just for the record, not all seinen is about external conflict. There's more seinen with internal conflict than there is josei with male authors. You say I made generalizations, but this is a generalization too.
Now let's look at ALL the aspects. This is non-romantic, male-gazey, has stereotypical seinen art and male authors.
Anyways, as I said in the original comment, this is all guess work since korean comics don't use these categories. This is listed in the original site as simply "story" and "thriller".                                            
                                                I see where you’re coming from, but I think you’re still over-relying on surface traits to define Josei vs. Seinen. A few extra points to consider:
   1. Psychological storytelling is strongly tied to Josei.
-While Seinen certainly can have internal conflict, its dominant identity (hallmark ) is still tied to external, plot-driven conflicts. This manhwa is driven almost entirely by psychological tension, manipulation, and emotional stakes! ( style much closer to classic Josei dramas than to Seinen’s structure)
   2. Josei doesn’t exclude darker or male-gazey works.
-Josei historically includes titles that are gritty, sexualized, and even exploitative at times. Flowers of Evil and Helter Skelter (both Josei) don’t shy away from using sexuality and discomfort through a female lens. Just because a story has “male gaze” elements doesn’t mean women aren’t the intended or engaged audience.
   3. Female-centered narratives are rare in Seinen.
-Regardless of outfits or camera angles, this story is still led by a female protagonist whose POV drives the narrative. Seinen rarely makes women the central subject without reducing them to side characters, trophies, or supporting roles. However , Josei, normally explores flawed, complex women as leads. That’s the mold this story fits.
   4. Market reception matters too.
-In practice, the readership skews differently. A webtoon like this is marketed on websites and platforms where it's predominantly female readers, which is part of why fans see it as Josei. If it were Seinen, it would likely be pushed alongside male-oriented action/fantasy thrillers.
   5. The “checklist” approach oversimplifies.
-Yes, the art leans Seinen-ish, yes, there’s fanservice, yes, the authors are male but none of these outweigh the main themes and intended audience. If anything, that mix just shows Josei is evolving and borrowing aesthetics from Seinen, rather than proving it “isn’t Josei.”
   6. Korean webtoons blur the categories anyway.
-Since you pointed out they don’t officially use these labels, all the more reason not to force-fit it into Seinen just because it has male authors or sharper art. If we’re applying Japanese demographic terms, then Josei is the closer fit because of its themes and focus, not Seinen.                                            

		
This is interesting, I don't think it's josei though. Seems like a "seinen" with a female protagonist. Quotation marks on seinen because this is a Korean webtoon so this is not how they classify things.