Tomoyuki Maruyama, also known by his stage name Kazuki Souya, is a Japanese voice actor from Tokyo, born on October 28. He is a graduate of the Production Ace Acting Institute and began his career with foreign film dubbing before moving into anime and game voice acting. He was formerly affiliated with the agency Production Ace but left in October 2020 to work as a freelancer, subsequently establishing his own official website in November of the same year. In 2021, he began using the stage name Kazuki Souya alongside his birth name, Tomoyuki Maruyama.

Maruyama has built a career characterized by a high volume of roles, often playing supporting characters, background voices, and distinctive side personalities across a wide range of anime series. He is known for his versatility, frequently voicing multiple different characters within a single show. One notable example is his role as Den Shinchuu in the Chinese-Japanese anime series Hitori No Shita The Outcast 2, also known as One-Hundred Thousand Bad Moments 2 or Hitori no Shita: The Outcast 2 Zensei Chapter. He is also credited as the voice of the character Hakase, which translates to Professor or Doctor, in the 2018 anime series Space Bug. His other prominent recurring roles include voicing various characters in the anime adaptation of the video game Megaton-kyuu Musashi, such as Koichi Sanuma and Tomoya Miyazawa. He has also been a consistent presence in the series Bofuri, voicing numerous minor characters across its first two seasons.

Beyond anime, Maruyama's career includes significant work in video games, providing the Japanese voice for characters like Travis Miles in Fallout 4 and Blitz in Rainbow Six Siege. He is also active in film dubbing for Western and Asian productions, with credits including voicing the Air Force Chief of Staff in Sonic the Movie and Daniel Ellsberg in The Post. In addition to his voice work, he holds qualifications as a licensed cook and a Shinto priest, and his personal interests include darts, billiards, and documenting his solo food experiences.