Watanabe Mutsuki is a Japanese scriptwriter from Ibaraki prefecture.

She graduated from Senshu University Faculty of Literature, the Graduate School of International Literature and completed a master's course. Her blood is type B.

After the scenario lecture of the Scenario Writers Association of the Japan Association, she became a scenario writer. She won the Setagaya literature award, Omorimo Shoji prize / honorable mention encouragement prize, TV Asahi 21st century fresh scenario grand prize excellent prize. Her character Tamagawa Doyle is a parody character of "Edogawa Conan," the main character of "Detective Conan.