Complex sentence: The show's protagonist has an unusually sensitive sense of smell that allows him to detect and distinguish trace amounts of various substances, which he uses to investigate crimes along side his childhood buddy, a major in the Special Bureau of Investigations.
Split into simpler sentences: The show's protagonist uses his unusually sensitive sense of smell, that allows him to detect and distinguish trace amounts of various substances, to investigate crimes. He works alongside his childhood buddy, a major in the Special Bureau of Investigations.