Agnes Tachyon is a student at Tracen Academy and a highly intelligent, eccentric horse girl driven by an insatiable curiosity to explore the outer limits of speed using science. She has short, messy brown hair with a prominent forward-leaning ahoge, and striking red eyes that lack typical highlights, instead containing horizontal grid-like patterns. Her height is 159 centimeters, and she was born on April 13. She embodies the archetype of a mad scientist, performing all manner of unauthorized and potentially dangerous experiments on living subjects with no regard for rules or personal boundaries. She often misses classes and races to prioritize her research in an abandoned classroom she shares as a hangout space. Despite her chaotic methods, she is not malicious; she has a playful, jovial, and eccentric disposition, speaking her mind freely and being direct, blunt, and occasionally rude. Her extreme focus on research means she cannot manage daily life without support, often neglecting basic needs like cooking proper meals or buying clothes that fit well. She has an intense sweet tooth, consumes large amounts of sugar, enjoys tea with plenty of sweetener, and hates bitter things. Her philosophy is that life is an experiment and all beings are its subjects. She develops two simultaneous plans: Plan A involves strengthening her own legs to reach the ultimate speed, while Plan B is to select another Umamusume to achieve it in her place. In the film Beginning of a New Era, she acts as the primary rival to Jungle Pocket, defeating her in the G1 Hopeful Stakes and the Satsuki Sho before announcing an indefinite racing hiatus due to a leg injury. This decision transforms her into an insurmountable specter for Pocket. She shares a complex relationship with Manhattan Cafe, constantly trying to recruit her as a test subject, while Cafe often refuses and helps get her out of trouble. She has a friendly relationship with Daiwa Scarlet, who admires her experiments and volunteers as a test subject. Her roommate is Agnes Digital; though not particularly close, they remain friendly. She refers to her trainer as guinea pig and subjects them to various experiments. Her career is marked by physical fragility, and she is called a legendary phantom Triple Crown winner. She excels in science and mathematics, remembers all experimental data with perfect recall, and conducts research comparable to graduate-level work in pharmacology, robotics, and virtual reality. In racing, she is an exceptionally talented front-runner suited for middle to long distances. Before each race, she meticulously checks temperature, humidity, body temperature, weather, and wind direction. Her racing outfit includes a long lab coat with bandoliers holding corked test tubes of glowing blue liquid, worn over a yellow sweater vest, black collared shirt, necktie, black pantyhose, and white heeled ankle boots. An earring shaped like the chemical structure of indane adorns her right ear. Her special skill is named U=ma². She cuts her own hair when it grows too long and has a plain black phone background to reduce nighttime screen glare.