The source has been running six years, and the ratings rose six weeks straight

The webtoon behind this drama began in May 2020 and has not finished. It has passed 190 million cumulative views and is still being drawn.

So nobody knows how the story ends — not the people making it, not the people watching. And yet the ratings have risen six weeks in a row, from 7.4% to 10.2%.

At a glance

The title first. The show is called Yubunyeo Killer (유부녀 킬러); most reports carry only the English rendering A Bona Fide Killer.

One row behaves differently from the rest — the source row. Every other value is settled; that one points at something still in progress.

An unfinished source means there is nothing to spoil

The first question people ask about a webtoon adaptation is usually the same one. Does reading the source first ruin it?

Here the question does not apply.

The webtoon started in May 2020 and is in its sixth year. The drama runs fourteen episodes and ends on 12 September. It finishes before the source does. The ending that arrives in September is one the webtoon does not yet contain, so no amount of reading ahead will tell you how the last episode goes.

This is not the usual shape. Normally a completed story queues like inventory and reaches the screen years later, and how that queue forms is laid out in the regression drama where only the hero knows the ending. Here the rule is inverted.

A curve that rises six times points past the premiere, not at it

There is something the table does not say: ratings do not distinguish whether these are the same people or different ones.

But the direction is uncommon. Far more often the premiere is the peak and the line drifts down — a cable Monday–Tuesday show that started the same month fell from 4.2% to 3.1%. Advertising and trailers pile viewers into episode one, and from week two only the ones who stay are left. To rise six times running, new arrivals have to keep landing on top of the ones who stayed.

Before setting this number beside figures from another country, check what it counts. Why terrestrial 10% and cable 3% cannot be measured with the same ruler is covered separately.

So if the source ending is not what lifted it, what did

The ending drops out as a candidate, because there is not one. Three candidates remain, and this article could not establish which was decisive.

First, the script. Kim Eun-hee wrote Signal, Kingdom and Jirisan. In most casting stories the writer's name is the line people read last; here it belongs at the top. That the original reports carried the actors and left this name out is the odd part.

Second, the seat the actors returned to. Gong Hyo-jin is back on MBC for the first time since The Greatest Love in 2011, and Sung Dong-il's gap is comparable. One show contains two people returning to the same broadcaster after fifteen years.

Third, the slot itself. The show cleared the previous Friday–Saturday drama's best rating in its first episode. That splits the question of whether the show rose or the slot did. What a Friday 21:50 position means is visible in the map of channels and time slots.

Weighing the three would require comparing other shows in the same slot, and that comparison is not in this article.

The day job builds a hostage, not a contrast

The standard line about double-life premises is that the wider the gap between an ordinary day and an extraordinary night, the more the genre delivers.

That is half of it.

A gap alone does not carry episodes. What the day job actually does is create something to lose. Once there is a family and a workplace, exposure costs her something, and from that moment every scene carries a price. That is why the highlight reel dwells on the husband's shock. The tension in this show is more likely to come from the living room than from a firefight.

Another observation travels with these shows: leads in their forties and fifties in action and crime series have become more common. The black comedy led by Kim Hye-soo and Cho Yeo-jeong from the same season belongs on that list. But explanations for why the trend arrived now are mostly guesswork, this article included — what is confirmed stops at the fact that several such shows exist.

What this means where you live

The show is mid-run, so some things you can do now and others later.

• Reading the webtoon now will not ruin the drama, because the drama finishes first. The reverse does hold, though: read it after the finale and you will watch the same characters take a different road
• Search Kakao's apps by the Korean title. The English rendering is not standardised, so A Bona Fide Killer may return nothing. Availability by country and the point at which chapters go paid differ per app
• Time conversion. Fri–Sat 21:50 Korean time is 19:50 in Vietnam, Thailand and Jakarta, and 20:50 in the Philippines, Malaysia and Singapore. That is the Korean broadcast clock, not your viewing clock
• MBC is terrestrial, so overseas release depends on per-title deals. There is no simultaneous worldwide drop the way a streaming original has. Which platform carries it has to be checked country by country

The two companion pieces look at the same question from the other side: the regression drama where only the hero knows the ending, and the case where the show carrying a finished source went down instead.

When episode fourteen airs on 12 September, Yu Bo-na's story ends. The webtoon will still be being drawn that week. So whose ending is the one that arrives that night?

Further reading

• The regression drama where only the hero knows the ending — what buying a still-running source costs
• Two ways to put a fan at the centre — the twelve-episode adaptation that slid
• What ratings count and what they ignore — before putting 10% and 3% side by side
• The map of Korean drama channels and time slots — what a Friday 21:50 seat is worth
• The black comedy that began the same season — another case in the same observation

Sources

• MBC — A Bona Fide Killer programme page
• Money Today — Gong Hyo-jin's action lifts 'A Bona Fide Killer' to a new series high
• Financial News — 'A Bona Fide Killer' hits 9.8%, a series high every week
• Topstar News — 'A Bona Fide Killer' reaches 10.2%, another series high
• Daum — Kakao Webtoon's 'Yubunyeo Killer' adaptation premieres on the 31st