Susumu Kotaki is the real name of Shinya Otaki, a Japanese actor and voice actor born on July 29, 1953, in Kanagawa Prefecture, Japan. He graduated from the Kanagawa Prefectural Oppama High School and the attached acting institute of Bungakuza. In his early career, he was affiliated with Office Hisu and Production Baobab before working as a freelancer. His voice acting career began in the 1980s, and he is known for his work in anime, particularly in Sunrise and robot-themed series, as well as for dubbing foreign films and television dramas. A notable example of his anime work from this period is the role of Tamashiro Nabari in the 1982 series Gyakuten Ippatsuman.

Otaki has portrayed numerous leading and supporting characters across a wide range of anime. He is particularly recognized for his roles in the Gundam franchise, such as Mezun Mezun in Mobile Suit Zeta Gundam, Arias Moma in Mobile Suit Gundam ZZ, and Doctor S in Mobile Suit Gundam Wing. His other prominent anime roles include Jiron Amos in Combat Mecha Xabungle, Granzort in Madō King Granzort, Kantam Robo in Crayon Shin-chan, the narrator in Ninku, and various characters in the long-running series Nintama Rantaro and Detective Conan. In addition to television animation, his film credits include Laputa: Castle in the Sky, Doraemon: Nobita's Wan-Nyan Spacetime Odyssey, and multiple Crayon Shin-chan films.

Beyond anime, a significant part of Otaki's career is in voice-over work for foreign films and television series, where he was the regular Japanese dubbing voice for Hong Kong actor Yuen Biao. His contributions to the industry also include taking over some roles from the late voice actors Kenyu Horiuchi and Katsuji Mori. His interests include pachinko, shogi, and golf.