Maddox Sogetsu, known in the Japanese version as Manabu Sogetsu, is a supporting character in Yu-Gi-Oh! Go Rush!!. He serves as one of the top agents of an organization called The Secrecy, also referred to as MIK, which is dedicated to monitoring and cracking down on aliens who come to Earth without proper authorization. Maddox is a tall boy with blue eyes and neatly styled purple-black hair featuring a distinctive ahoge. His fringe is styled into a point, and he bears a strong resemblance to his descendant, Gavin Sogetsu, from the previous series. He is frequently accompanied by his alien cat partner, Meowdestar.

Born as the heir to the Sogetsu Style, a family tradition that blends martial arts with dueling, Maddox underwent intense training in various forms of combat. However, he harbored a dislike for using his skills to hurt others. During his youth, he met a character named Graves and would play with him to escape the rigors of training; this led to his instructors sending him away to the mountains for further discipline. These experiences shaped his initial personality as a strict, duty-bound agent who follows the rules of The Secrecy without question.

In the story, Maddox first appears as an antagonist to the main characters, particularly Yudias Velgear, attempting to enforce the organization’s regulations on aliens. After Yudias defeats him in a duel, Maddox keeps his word to leave him alone as long as he causes no trouble. This defeat marks the beginning of his character development. In the second season, he becomes increasingly conflicted between his loyalty to his friends and his obligations to The Secrecy. He eventually joins forces with Yudias, Yuamu, and Yuhi after the antagonist Phaser Ryugu takes over MIK, demonstrating a shift from a rigid enforcer to a more flexible ally. His personality is also noted for being a chemical otaku with a cat mania and a unique way of speaking, adding layers to his otherwise disciplined demeanor.

Maddox utilizes the Sogetsu Style of dueling, which incorporates chemical and cybernetic themes, allowing him to employ cards that reflect his analytical and methodical approach. His notable abilities include a talent for combining martial arts concepts with Rush Duel strategies, making him a formidable opponent. His key relationship is with Meowdestar, his constant partner, and he forms significant bonds with the main trio over the course of the series, evolving from a primary obstacle to a trusted comrade.