There are many, many ways Yasuko Kobayashi defies the expectations of the genres and franchises she works on. Here are just a few examples.
Note: The lists below are based on assumptions made through observing her various works.
Kobayashi doesn't seem to like playing a trope straight, especially if it's related to an important point in the story. When she's the lead writer, there can and will be subversions, plays, double-subversions, aversions and pretty much anything under the "Playing With" category, in any possible order and combination that fits the situation. Once you've become familiar with her works, it makes you wonder if she has something against trope "norms" and clichés...
"Show, Don't Tell" is the mantra. It will be a main element in her stories. She won't tell you anything outright, and instead convey through hints, dialogues and character emotions.
Kobayashi will have multiple plot threads going on, but she'll focus mainly on two - one main and one background, going on at the same time.
Lots of characterization: definition, exploration, development,... This is especially prevalent in her Tokusatsu works, which turn out to be more than just Battle-of-the-Week routines.
In a Five-Man Band, characters are almost guaranteed to be of different backgrounds and philosophies. Don't expect them to get along immediately; that's always for Character Development.
Especially evident in Timeranger and Shinkenger. In fact, Shinkenger makes the band not knowing each other a rather vital part of the series, as each of the Samurai Sentai's number have their own issues and secrets. Making them unknowns to each other to start, and even putting a gulf of seperation in time between the two that are childhood friends, allows us to discover the characters as they do, bit by bit.
In fact, Kobayashi could be said to practice Jigsaw Characterization along with her plotting.
Hints of a Bittersweet Ending in varying amounts, depending on the series. Even if the ending is mostly optimistic, there'll most likely be at least a sad subtext in the whole series' context.
As seen in the endings to Ryuki, Timeranger, Den-O, Blassreiter, Shinkenger and OOO.
The majority of her earlier works have been Darker and Edgier, but it's not generally a guarantee; with Den-O and Shinkenger, she's also proved that she can handle humor rather well. This doesn't seem to apply to her Anime works so far though.
As a rough rule, don't expect regular romance in her stories. If there's one, she's already plotting something to do with it...
On the other hand, she doesn't seem to mind throwing some Ship Tease now and then, when it fits the atmosphere.
May have some I Work Alone tendencies as the lead writer; this is especially notable if you look at the episode credit tables for each series on Wikipedia Japan. The plus side is that this gives the stories very fluent consistency.
One astonishing instance is with Shinkenger, where out of 49 episodes, only 7 of them are written by sub-writers, all side episodes. Meaning? She wrote the other 42 singlehandedlynote And probably literally, too..
It still doesn't beat Den-O, though; 45 out of 49?!? ...Damn.
However, even Den-O doesn't beat Kobayashi's work on Pretty Guardian Sailor Moon, where she wrote every single episode and both of its specials.
Kamen Rider OOO: 38 out of 48. Fewer than other series she wrote, but she still took care of most of the plot-important episodes.
"She Changed It, Now It Sucks/Rocks", and VERY much so. Due to her habit of throwing in elements and concepts never/rarely used before, the audience's initial reception of her stories tend to range from lukewarm to cold. But for the very least, it's safe to say that her works are quite popular in Japan.
The most triumphant example: When Kamen Rider Ryuki aired, the massive load of liberties she took pretty much almost derailed it from being a standard Kamen Rider title, and this threatened the show's ratings for a while, almost to the brink of cancellation. But the audience slowly became engrossed in the storyline after the hungover passed. And indeed, the following Heisei Kamen Rider stories having a variety different concepts and formulas can be partially attributed to her breaking down the barriers - perhaps in conjunction with Agito.
And then, in an interview while she was working on Ryuki, she says she's never seen a Kamen Rider series before...
Not to say Kobayashi doesn't have a few favored themes and Aesops. While her protagonists often must deal with the fact that there are things beyond their control, the reccuring answer is that they decide how to deal with it — she's a big fan of Earn Your Happy Ending. Even when it's really Earn Your Bittersweet Ending.
Jigsaw Puzzle Plots. She always goes extra lengths to set up intricate stories, split them up into tiny little bits, shuffle them thoroughly and drops piece by piece in front of the viewer one at a time. And really darn good at it.
Kamen Rider Ryuki is a prime contender among her Tokusatsu works all Heisei Kamen Rider series.
Tends to pick Nice Characters as leads; so far, pretty much every main character she created herself.
In fact, her most common trope is to put such a sweet/nice character in adverse situations that they almost don't deserve, and have them overcome it over the story's course. As long as they don't run into a Bittersweet Ending.
She's among the few Tokusatsu writers that can weave all the merchandises into their source series while averting blatant advertising, as well as assigning them appropriate significance in the series. Yes, she can dignify merchandises in-series.
She also has a tendency to weave technically accurate scientific conventions into her stories when they're required. Timeranger follows a quantum mechanics model in its usage of time travel, while Den-O makes extensive use of real theories about singularities.
Taking the most basic assumptions about Kamen Riders: Riders are allies of justice? Not in Ryuki. Instead, we get 13 Riders (there hadn't been more than 3 Riders in a series before this). And they're less concerned with justice and more with an Elimination Battle Royale against each other. And the candidates in the Rider war are hardly typical Riders. We have:
Who says Riders need to be tough, manly men? Here, we have the most softspoken and innocent pushover of a lad with the worst fortune in the world as the main Rider. As well, after several seasons of dead serious Kamen Rider shows, in Den-O we have somelots of humor— so much so some fans on both sides of the Pacific were left kind of off balance.
The source of Rider powers have been mostly from science, and a few from mysticism. Here, we have Demonic Possession. Featuring a boy and his five time-traveling demons.
And while she's at it in that recurring theme of Kobayashi's on dealing with what you can control and accepting what you can't, she manages to take a hammer to You Can't Fight FateandScrew Destiny.
Super Sentai has been highly theatrical ever since its beginnings. Here, we see that turned Up to Eleven as Kobayashi marries Sentai to Jidai Geki. It is a very happy marriage, and you even see the influence of Kabuki as implied by one of the character's backgrounds.
Kobayashi also gets her favorite theme of earning things in adversity in early— the members of the Shinkenger are at varying degrees of skill and bring vastly different attitudes to that training. This leads, more often than not, to that oh so prized clash of personalities she mines to bring out the rich characterization she's known for.
Something that was a major theme in Den-O becomes even more important here— the concept of True Companions. Who are you loyal to? Why? What makes you worth the loyalty others give you? What's the difference between duty and friendship? All these questions are considered over the course of the series, and the climax throws them into stark focus.