During June 2025, wkdtk85 focused on enhancing documentation for core data structures in the krafton-jungle/KJ-DS-BOOK-9-303 and KJ-ALGO-BOOK-9-303 repositories. They delivered detailed Markdown guides on hash tables and tree data structures, clarifying concepts such as collisions, load factors, and advanced hashing techniques, while also distinguishing trees from graphs with practical examples. Their technical writing and computer science fundamentals ensured the documentation was accessible and accurate, supporting faster onboarding and self-service learning. By refining terminology, improving readability, and restructuring content, wkdtk85 provided a solid foundation for learners and engineers to deepen their understanding of algorithms and data structures.