Set after the fourth film, the show follows 11-year-old Keisuke Amano, the younger brother of Natsume (both are offspring of Keita Amano and Fumika Kodama from the original Youkai Watch anime). Keisuke is skeptical of the supernatural world until he notices his sister's frequent late-night returns. Curious, he follows her and discovers she's been exorcising evil Youkai with her friends Touma and Akinori while running a Yo-Kai detective agency. Natsume reveals their secret to Keisuke and allows him to join in their activities as they investigate Youkai crimes and fight off evil Youkai to maintain peace in the city.