[2] Yasui was born in Ishima Village [ja], Mitsu District, Okayama Prefecture.

After graduating from the Faculty of Law in Tokyo Imperial University, Yasui joined the Home Ministry, where he served as superintendent for Ibaraki and Kanagawa police.

[3] In 1931, Yasui became a secretary to the Governor-General of Korea, Kazushige Ugaki, and served in colonial management, including the head of the Monopoly Bureau (朝鮮総督府専売局).

He served alongside Keiko Asanuma, Eiichi Tanaka, and Hyō Hara.

[2] On 9 January 1962, he was made an honorary citizen of Tokyo due to his contributions to the city.