TV-Series
Description
Taro Hirai is a young student residing in the same boarding house as Kyosuke Kindaichi. He has paused his formal education to pursue his ambition of becoming a novelist and is actively writing a novel. Hirai possesses ochre-colored hair and brown eyes, with some sources describing his eyes as pastel purple.

He exhibits highly analytical thinking and deduction skills, noted to surpass those of many adults. Hirai actively participates in gatherings with literary figures at establishments like the Milk Hall (Kikunyusha), where Takuboku Ishikawa shares details of his detective cases.

Hirai plays a significant role in solving the murder case of Otaki at the Hananoya brothel. He reveals he secretly followed Ishikawa and Kindaichi to the red-light district that night, witnessing key events. By examining Ishikawa's notebook left at the crime scene, Hirai deduces that Otaki's death was a suicide motivated by her terminal illness and unrequited affection for Kindaichi, clearing Kindaichi of false murder accusations.

His deductive contributions continue in other investigations, such as assisting Kindaichi in deciphering coded messages related to a theft case during Ishikawa's temporary estrangement.

The character is based on the real-life Japanese author and critic Tarō Hirai (October 21, 1894 – July 28, 1965), known widely under the pseudonym Edogawa Ranpo. This connection is subtly referenced when Ishikawa rewards Hirai with a two-sen coin after solving a case, alluding to Hirai's future 1926 work "The Two-Sen Coin".