Saito developed a broad and specialized set of skills working for 16 years at Japan's largest law firm, Nishimura & Asahi. During that time he focused on specialized securitization, credit derivatives, Basel capital finance, Islamic finance, and construction project finance.
He wound up as a foreign intern at New York based international law firm, Debevoise & Plimpton and later started lecturing about securitization at the Chuo Graduate School of Accounting.
In 2013 Saito happened across his first digital currency case and it would change the course of his work. During Mt. Gox's bankruptcy, Saito had the opportunity to work with the government discussing regulation of Bitcoin. Shortly afterwards he opened his own practice specializing in cryptocurrency, blockchain, and fintech. Since then he's also been a legal advisor to the Japan Blockchain Association, a corporate auditor of Topaz Capital, a corporate auditor of Mitsubishi Jisho logistics REIT, and a director of Cedyna Servicer. In 2015 he became an external director at BitFlyer, a Japanese cryptocurrency exchange.