Tatsuya Hirai is a Japanese male voice actor who has worked extensively in adult visual novels and anime since beginning his career in 2003. He is also known by a previous stage name, Masumi Hirai. Hirai is publicly known to be a pseudonym of fellow voice actor Daisuke Hirakawa, which he uses for performances in adult-oriented media.

Hirai is best known for his portrayal of complex and often dramatic leading characters. His most notable role is Makoto Itou in the School Days series, a character he voiced in the original visual novel and its associated OVA adaptations. This performance brought him significant recognition within the industry. He also voiced Kazuhiko Amamiya in the OVA series Taboo Charming Mother, a role that was among his early, career-establishing works.

His filmography includes a range of characters in both games and anime. He is credited as the voice of Chihiro Konno in the anime Kuro to Kin no Akanai Kagi and as Yahiro in the OVA Shinobi Seduction. Hirai is also recognized for his work in the Boys Love genre, with prominent roles such as Katsuya Saeki in Kichiku Megane and Ivan Fiore in Lucky Dog 1. His repertoire extends to otome games, where he voiced characters like Mizuto Nomiya in Chou no Doku Hana no Kusari.

Throughout his career, Hirai has been frequently cast in emotionally charged and versatile roles, from dramatic leads to nuanced supporting characters. His work is characterized by a high degree of collaboration on specific series, often reprising his roles across multiple game sequels, anime adaptations, and drama CDs. Notable examples of this include his continued performances as Makoto Itou in the School Days and Cross Days games, and as Katsuya Saeki in the Kichiku Megane series.

While he has not received major public industry awards, Tatsuya Hirai is considered a prominent and respected figure in the niche of adult visual novel and BL game voice acting. His performances are consistently praised by fans for their emotional depth, range, and ability to bring memorable characters to life, solidifying his status within this dedicated community.