This monograph provides the first formal academic definition of TRANSPLEX, a new electronic music genre established in 2025 by Akihisa Yorozu (AY Sound Works). TRANSPLEX integrates the structural clarity and euphoric build-ups of Trance with the fragmentary timbral dynamism of Complextro, while explicitly addressing their respective limitations. Grounded in information theory, cognitive neuroscience, and music psychology, TRANSPLEX is defined as a genre constrained by an optimal complexity zone, balancing predictability and novelty. This document presents the theoretical framework, formal definition, comparative analysis, and implications for musicological classification. It is intended as a permanent academic record, archived with a DOI.