Anime drug police pretend to be husband and wife. Who is undercover?

Black without a horse, white without a horse. According to Douban.com, in the anime "Black and White", Xiaohei's sister, Black and White, pretended to be a husband and wife undercover as a drug policeman. The cartoon "Black and White" is adapted from Yu Yanshu's original cartoon with the same name, and is produced by Giant Panda Animation Studio.