It's weird: Just as midsize sedans fall out of fashion, there's never been a better time to buy one. Segment leaders like the Honda Accord and Toyota Camry are the best they've ever been, to say nothing of stylish alternatives like the Hyundai Sonata and Mazda6. Kia's been a longtime player in this space with its Optima sedan, but it's poised to make an even bigger splash with the launch of that car's replacement. Say hello to the new K5.

Before I get into the nuts and bolts of Kia's new four-door, let's talk about that name. K5 is what the Optima was always called in its home market, South Korea, where Kia uses a Kx naming strategy for its sedans (our Forte is known as the K3, the Cadenza is the K7, the K900 is -- you guessed it -- the K9). "This new car is such a big departure from the outgoing model that we thought it deserved its own name," a Kia spokesperson tells me. No, this doesn't necessarily mean Kia will be switching to any sort of whole-line alphanumeric naming strategy in the US, though the same spokesperson says that's not out of the question if future products "meet this same high standard."

Never mind the name; just like the Optima, the K5 is a lot of car for the money and this model makes a strong statement right off the bat. Its design is more refined than the Hyundai Sonata, though the Kia lacks some of its kissin' cousin's clever details, including the Sonata's daytime running lights that blend into the chrome trim running. Still, the K5 gets a lot of things right: Its clamshell hood means there's no unsightly cut line across the nose, the bright roofline accent wraps down below the rear window and the full-width LED taillights are broken up into segments of different lengths for some rump-end visual interest. It's not perfect, of course. All of the the creases come together at the corners of the K5's face and, to my eyes, it looks like someone wearing poorly fitted pants that bunch up by the crotch, an impression emphasized by the running-light signature that doubles as the turn signals. Oh, and pretty much all of the vents are fake, which is a Hyundai/Kia styling trend that cannot die soon enough.

In profile, the K5 almost looks like it should be a liftback -- not unlike Kia's larger Stinger -- but it's got a conventional trunk with 16 cubic feet of space. Base LX models ride on puny 16-inch wheels, but the uplevel LXS, GT-Line and EX trims get the attractive 18-inchers seen here. Speaking of which, you'll notice two different K5s pictured in the gallery; the gray car is an EX, while the red one is a GT-Line. The latter gets a couple of unique design elements including LED foglights, larger (fake) vents on the rear flanks, a small decklid spoiler and a black roof. But don't let these sporty-ish cues fool you. Underneath the skin, the GT-Line and EX are identical.

The K5 LX, LXS, GT-Line and EX models share the same powertrain: a 1.6-liter turbocharged I4, with 180 horsepower, 195 pound-feet of torque and an eight-speed automatic transmission. Front-wheel drive is standard, but the LXS and GT-Line can be had with all-wheel drive -- a smart move, considering the Nissan Altima, Subaru Legacy and Toyota Camry are now also offered with this foul-weather capability.

In both the EX and GT-Line, the 1.6T is tuned appropriately. It's neither particularly peppy nor sluggish, with all of its torque delivered from just 1,500 rpm. That means there's ample power for around-town driving and the transmission doesn't have to kick down multiple gears in order to provide adequate oomph for passing. This also helps the engine run as efficiently as possible and, to that end, the K5 posts excellent EPA-estimated fuel economy ratings. A base LX should return 29 miles per gallon in the city, 38 mpg highway and 32 mpg combined, while larger-tired LXS, GT-Line and EX versions are slightly less efficient, at 27 city, 37 highway and 31 combined. Add the aforementioned all-wheel drive and you're looking at 26 city, 34 highway and 29 combined.

A more powerful K5 GT will hit the road later this year with unique chassis tuning, 19-inch wheels and -- most importantly -- a 2.5-liter turbo I4 engine with 290 hp, 311 lb-ft and an eight-speed dual-clutch transmission. Consider this Kia's version of the Hyundai Sonata N-Line, a car my Roadshow pal Antuan Goodwin drove in prototype form late last year.

Buyers looking for an entertaining midsize sedan will likely want to wait for the GT. The standard K5 models offer solid on-road manners, but they aren't what I'd call sporty -- not that they need to be. The K5 will spend the majority of its life on commuter duty and it's nicely tuned for that purpose. The steering is light (if a tad overboosted) in the car's default drive setting, but if you dial up Sport, a noticeable -- and appreciated -- bit of weight is added to the wheel's action. Body motions are smooth and controlled and the K5 handles corners with more poise than an Altima, Camry or Legacy. I'm also happy to report that the US-spec K5's brakes are easy to modulate, with progressive initial bite -- much better than what my other pal Andrew Krok experienced in an early Korean-spec model in Seoul last year.

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Overall, the K5 falls somewhere in the middle of the class as far as driving dynamics and engagement are concerned. The Honda Accord and Mazda6 are more fun, but I'd rather drive the Kia than a Nissan Altima or the aged and irrelevant Chevrolet Malibu, a car I thankfully won't have to talk about for much longer.

Where the K5 really sets itself apart from the class is inside. Like its Sonata corporate sibling, the Kia K5 has a stylish cabin that's downright luxurious in higher trims. In my EX tester, soft leatherette seats are met with nice-looking wood on the dash and all of the switchgear looks and feels great. Yeah, there are a few questionably cheap bits of plastic trim on the transmission tunnel and door cards, but it's nothing too egregious. Weirdly, though, the electronic gear selector dial seen in the Korean-spec K5 isn't available here -- you get a standard PRNDL shifter, but given the inherent ease-of-use factor, that's not a complaint.

Front passengers have plenty of headroom and the K5 feels open and airy, even with the panoramic sunroof shade closed. The rear seats are just OK, the sloping roofline means taller folks will need to duck to get in or out and the back isn't as spacious as some of the K5's competitors. The upward slope of the beltline and fastback-style rear window hurts visibility, too, though most people just rely on the standard backup cameras these days.

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The K5 offers lots of multimedia tech, but there's one big head-scratcher: The standard 8-inch UVO touchscreen infotainment setup features wireless Apple CarPlay and Android Auto. But if you want the larger 10.2-inch screen with its better graphics and additional features, you're stuck with a wired connection for the smartphone-mirroring tech. Kia recognizes that this is odd, though the company isn't offering any sort of explanation. Furthermore, Kia says there are no plans to update the 10.2-inch experience to include wireless connectivity. So it goes. Thankfully, no matter the screen size, UVO is super responsive and easy to navigate, plus there's an optional wireless charging pad that's housed in a convenient little slot just ahead of the center console.

Driver-assistance tech is in similarly high supply, though most of the good stuff is only available through option packages on higher trims. Forward-collision warning, lane-keeping assist and automatic high beams are standard, but you'll have to step up to the LXS to get blind-spot monitoring and rear cross-traffic alert. On the GT-Line, a Premium Package gets you adaptive cruise control, but it doesn't include lane-keep assist. For that, you have to get the EX with its Premium Package, which unlocks Kia's Highway Driving Assistant, bundling full-speed adaptive cruise control with lane-centering tech to make highway commuting a lot easier.

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A base 2021 Kia K5 LX comes in at $24,445 including $965 for destination, while a fully loaded, front-wheel-drive EX like my tester rings up for $32,355. The GT-Line I also sampled, meanwhile, comes in around $28,000. Across the board, the K5 is competitively priced within its class -- even the forthcoming GT will top out just under $36,000 with all the option boxes checked.

The 2021 Kia K5 isn't the best at any one thing, but it does everything a midsize sedan should. The Mazda6 is more fun to drive, the Accord is more refined and the Hyundai Sonata offers a little bit more in the way of trick tech. But as a fully baked package, the K5 is a big step forward for Kia -- an optimized Optima, if you will -- and that makes it yet another compelling option in this increasingly overlooked class.