During January 2026, Jihun Kim focused on backend stability for the BCSDLab/KOIN_API_V2 repository, addressing a critical issue with timetable lecture data integrity. He identified and resolved a bug that caused duplicate entries during timetable deletion flows, which could have led to downstream inconsistencies. By updating both repository and service layer logic, he ensured that multiple timetable lecture entries were handled correctly, preventing the creation of orphaned or redundant records. His work standardized data access patterns for bulk and delete operations, leveraging Java and the Spring Framework to enhance reliability and maintainability in the backend system throughout the development cycle.