Marathon is a lightweight, mid-size Steelframe designed by Uccello Engineering, a Venusian motor company specializing in high-performance automotives. Sacrificing creature comforts for an efficient weight profile, Marathon's silhouette appears almost skeletal compared to other Steelframes, but it should not be mistaken as underprepared to succeed in its niche- Marathon is built to go as fast as possible at ground level and navigate uneven terrain verticality that would prove insurmountable for a wheeled or tracked vehicle. It achieves this by sporting long, slender arms that make climbing and lifting its own lightweight frame easier than more contemporary Steelframes- they could simply use their boosters to fly over obstructions, but Marathon is built to comply with the spirit of Ferry's pan-Solar rally races, so flying is out of the question. To allow it a better grip on natural handholds, Marathon's finger joints are designed with a strong, cord-like grip actuator that translates tensile strength into sturdy gripping power. These finger joints are sheathed in textured polymer sleeves, affording Marathon the sort of fingertip gripping strength one might find in organic lifeforms. Its forward headlight array is situated on either side of its cockpit, with its lights protected from debris moving at high speeds by a set of retractable covers intended to prevent impact damage to their bulbs when not in use. Its ankle, hip and shoulder joints are the largest of its articulation points, giving it the most power in the most important places to push and pull itself along the ground. Its cranial sensor array is somewhat limited compared to other model Steelframes, offering little more than a visual sensor with thermal and ultraviolet lenses, an on-board integridometer and a satellite relay antenna coiled around the interior of its aerodynamic, dome-shaped head. Internal software converts sensor data into a short-range topographical map that Koichi can consult from the cockpit, but any purpose-built mapping antenna array has been omitted in the spirit of winning a race in the most honest and indisputable means possible.
The real sauce behind Marathon's design, however, is in its unique foot and propulsion engine synergies. Since it competes in ground-level rally races, Marathon is capable of running at a fast sprint, its footfall nimble enough to step across stones to clear a running river, but when it comes to stretches of flat, open terrain, Koichi is able to flip on the boosters and really let it rip. Marathon sports a pair of Mercurian-made ITA-46000 "Skullripper" ionic thruster engines capable of putting out an extreme amount of go-fast juice channeled mostly in one direction. To make the most of these engines, Marathon's foot units feature a set of wheels that can be deployed from the top to the bottom of its tarsal blades, their ball-bearings allowing Marathon to skate along under the force of its own propulsion, quickly switching from a running-and-climbing mode to a high-speed straightaway mode. Radial brake calipers are located inside the tarsal blades to stop these wheels from spinning when needed, but a pivoting lateral skid is a more balanced way to brake from high speeds than simply seizing the wheels up beneath it. Maneuvering Marathon in this propulsion mode is a lot like riding skis or inline skates in the manner of a cartoon animal doing so with a gigantic red rocket strapped to their back, it requires a particular amount of finesse that really puts a Steelframe pilot's neural implant to good use. The Steelframe can angle itself in a low crouch using its robust tarsal articulation points to really maximize its chassis' aerodynamic profile, with a sturdy set of shock absorbers to help mitigate the bumps it might encounter propelling itself forward in this manner- it's not a comfort for the pilot, mind you, but a way to prevent the Skullrippers from being bounced in a direction Koichi doesn't want them to go in.
Steering is largely handled through a set of six counter-thrusters built into its forearms and its lower legs, adding additional thrust points to help steer and stabilize the tremendous force propelling it from behind. Compared to other Steelframes, Marathon surrenders a full 360° pivot and rotational jet profile in favor of a mega helping of "go fast in this one particular direction." While it doesn't sport a traditional forcefield projection system, Marathon wears its protective armor plating mostly on its front side, to help minimize weight by efficiently protecting its chassis from debris and other impact events in the main direction it intends to be moving most of the time. Forcefield projectors would be a useful inclusion, but they would also draw power away from those Skullrippers, so in the name of efficiency they have been omitted from the design. Being highly specialized for grounded movement in gravity-rich environments, Marathon struggles a bit with underwater and zero-G navigation. While it can walk across lake beds and blast itself out of the water just fine, its lightweight chassis can't tolerate crushing deep-sea atmospheric pressures; similarly, due to its purpose-built go-go thruster design, Marathon isn't really built for using light little puffs of air to rotate and position itself while free-floating in space either; its powerful thrusters are so tightly calibrated for maximum performance that even a light twist of the throttle would be enough to send the Steelframe careening off on a long arc without a good way to counter-stabilize itself. Whoops! Koichi isn't ex-military, he's not a salvage operator and he's not a heavy industrial professional, he's a racer, and his machine does exactly what he needs it to in the environments he expects it to perform in. That performance just isn't really achievable without making significant compromises to the generalist nature of a standard Steelframe.
Koichi's oddball solution to pan-Solar rally racing is certainly a crowd favorite which stands out even among a diverse gallery of crowd favorites. Having a pair of wheeled feet allows Marathon to pass directly over other cars on long straightaways by simply drifting its feet around them, but also allows other racers an opportunity to downshift and lurch forward right between Marathon's own feet all the same. Having just two parallel wheels makes drifting corners a bit difficult for Marathon, but having the ability to jump, climb and even put one foot up on a wall with the other on the ground to take an outside turn that would scuff the paint off a traditional car gives this unique Steelframe some one-of-a-kind options for navigating twisting roadways populated by other drivers. In the event of a collision, it's able to roll other cars and set them rightside-up on the ground again, although its slim chassis might struggle to lift some of the heavier machines in the circuit. Koichi has a couple circuit wins under his belt- Phobos 2383, Enceladus 2385, Oberon 2388- he doesn't use his Steelframe to cheat other racers out of a fair opportunity to win and he hates to take a freebie, so he has been known to stop racing to right a vehicle that has been flipped upside-down so he can beat it fair and square. He wants his wins to be unequivocally earned by his own methods, in ways that stand up to meticulous scrutiny. He is an arrogant Android in an arrogant Steelframe, but he is arrogant in a fair way. When Marathon crosses the checkered line, no one can discredit the victory as coming from the underhanded use of a Steelframe; when Marathon crosses the line, it was Koichi's immaculate skill that made it happen.