Masaru Hamaguchi is a Japanese entertainer primarily known for his work as a comedian and television personality, who has also taken on a limited number of voice acting roles in animated projects. Born on January 29, 1972, in Osaka, he is one half of the popular manzai comedy duo Yoiko, which he formed with his partner Shinya Arino in 1990. His career has been predominantly in live-action television, where he gained widespread recognition for his appearances on variety programs like the long-running series "The Legend of the Golden Era".

Hamaguchi's foray into voice acting is closely tied to his celebrity status. He voiced the lead role of Dr. Hamax in the 2007 television anime series "Tensai? Dr. Hamax". This 12-episode series, which aired on the Family Gekijyo channel, was built around Hamaguchi's comedic persona, with his regular comedy partner, Shinya Arino, also providing a voice for the show.

Prior to this, he took on the role of Cain in the 2006 animated science fiction film "Origin: Spirits of the Past" (also known as "Silver-Haired Agito"). Produced by the animation studio Gonzo, the film featured a cast composed largely of well-known actors and celebrities, with Hamaguchi's voice work being part of this trend. In the English-language dub of the film, his character was voiced by actor John Burgmeier.

Beyond these two prominent credits, his voice acting portfolio includes minor roles in other animated works. He provided a voice for a pair of twin brothers in the anime "Kuma no Pūtarō" and, in later years, took on small guest roles in series such as "PriPara" and the "Tomica Kizuna Gattai: Earth Granner" franchise. His contributions to anime voice acting are thus an extension of his broader entertainment career rather than a primary focus.