Height: 176cm (5'9)

A Japanese actor, voice actor, singer and narrator from Shiogama, Miyagi Prefecture. He graduated from Tohoku Gakuin University's economics school and is currently affiliated with Across Entertainment.

He was the manager of the Tagajou Senior High School basketball team before he made a name for himself. His voice acting debut was the OVA Megazone 23 as the motorcycle-riding Shinji Nakagawa, while his television debut was the anime Bosco Adventure as the cowardly Otter. His break-out role, however, was in the anime Ranma ½, in which he played the dual role of Hibiki Ryoga and the Jusenkyo Guide. In 1991, Yamadera joined forces with Toshihiko Seki and Noriko Hidaka to form the acting unit Banana Fritters, which disbanded in 1995. In October 1997, Yamadera became a host on the TV Tokyo children's variety show Oha Suta. In March 2016, after almost two decades, he announced his retirement from it.

Yamadera's also known for his versatile range, as shown in the video game Danganronpa V3: Killing Harmony where he voiced all five Monokuma Kubs, including Monophanie (female). According to the Danganronpa V3 official blog, Yamadera is the first person who came to mind as "the same person voicing multiple characters at the same time". No one has as much "multiple characters" experience as him. He was able to take the individual quirks of each of the Monokuma Kubs and make all of them unique.

Other notable examples of multiple voice acting include the Kingdom Hearts series where he voiced Donald Duck, Genie (Aladdin), Sebastian (The Little Mermaid), Beast (Beauty and the Beast), Mushu (Mulan), Jaq (Cinderella) and Stitch (Lilo and Stitch), Shun Akiyama (Yakuza), and the Japan Animator Expo series of 35 short films where Yamadera and Megumi Hayashibara voiced all characters.

Yamadera was married to fellow voice actresses Mika Kanai from 1993 to 2006, and to Rie Tanaka from 2012 to 2018. On June 14, 2021, his marriage to singer and idol Robin Shoko Okada was announced.

Trivia:

• His nickname is Yama-chan.
• The official dub-over voice for Eddie Murphy, Jim Carrey and Disney's Donald Duck.
• He didn't consider to do voice acting at first and was more interested in being either a live-action actor or a salesman.
• He is known as "the man with the seven-colored voice".
• In 2011 and 2017, TV Asahi conducted a poll among Japanese voice actors and actresses on "who they thought was really the most amazing person in their profession". Yamadera ranked first both times.