Kōhei Amasaki is a Japanese voice actor born on October 22, 1990. He is affiliated with the talent agency I'm Enterprise. He began his professional career in 2014, taking on minor roles in anime and drama CDs, and his first starring role in a television series came in 2018 when he voiced Kirill Vrubel in Double Decker! Doug & Kirill. A native of Osaka Prefecture, he completed his training at the Japan Narration Acting Institute before joining I'm Enterprise in 2013.

Amasaki's career is marked by a wide range of roles across various anime franchises. In the late 2010s, he gained recognition for his performances as Haruo Yaguchi in Hi Score Girl, the passionate protagonist obsessed with retro gaming. He also began voicing recurring characters in major long-running series, such as the boastful student Neito Monoma in My Hero Academia and the shrewd merchant Otto Suwen in Re:Zero - Starting Life in Another World. His work in the music-focused multimedia project Hypnosis Mic -Division Rap Battle-, where he voices Saburō Yamada as part of the Buster Bros!!! unit, showcased his singing and rapping abilities.

His versatility extends to a variety of other prominent roles. He has lent his voice to Taichi Nishimura in Isekai Cheat Magician, Albert in Banished From The Heroes' Party, Jim in Love of Kill, and Edward of Westminster in Requiem of the Rose King. In film, his early work included a role in the 2015 movie The Anthem of the Heart. In the 2020s, he has taken on further leading roles, including Masachika Kuze in the romantic comedy Alya Sometimes Hides Her Feelings in Russian and the determined Will Serfort in the fantasy series Wistoria: Wand and Sword. His filmography also includes contributions to video games, such as Kanata Hjuger in Tales of Crestoria and Clanne in Fire Emblem Engage.

In recognition of his early career achievements, Amasaki received the Best New Actor Award and the Singing Award at the 13th Seiyu Awards in 2019. He has continued to receive recognition for his performances, including a nomination for Best Voice Acting Performance - Male at the Anime Trending Awards in 2025 for his role in Wistoria: Wand and Sword. With a career encompassing over a hundred roles, he is known for his energetic and youthful vocal quality, often portraying teenage and young male characters with a wide emotional range.